Purpose Religion has always been an important part of human civilization and has largely determined its paths. When speaking of tourism, religion has been one of the oldest motives for traveling. That kind of traveling found its place in the complex mechanism of touristic migrations as a selective tourism type called religious or faith tourism. Although Croatia as a country full of historical and art valuables has great potential for further religious tourism development, there is a lack of scientific and objective analysis of this specific area. Like any other form of selective tourist offer, it is also required to manage religious tourism in order to ensure efficient and sustainable economic development. Therefore, it is necessary to explore the religious tourism destinations, to look at the parameters that influence the effective synergy of the religious tourism destination factors, and to consider the needs of guests - religious tourists, in order to ensure positive economic effects with sustainable development in the destinations. Accordingly, the focus of the planned research is to find an optimal model for strategic management of religious tourism destinations. Methodology Various different methods of scientific research and suitable combinations thereof are employed when conducting scientific research, formulating and presenting results relevant for the defence of a doctoral thesis. For the empirical part of the research, a scientific model for the development of religious tourism was formulated and tested. Scientific research, formulation and presentation of research results in this doctoral dissertation has been accomplished by application of general methodological principles, commonly used in economic research. Acquired data has been analysed using methods of descriptive and inferential statistics. For the purpose of examining the sample of respondents that participated in conducted surveys, distributions according to gender, age groups, marital status, household income, employment status and degree of education have been determined. Distribution according to place of residence has also been determined for respondents who have gone on a religious journey at least once and responded to the survey. Distribution of respondents according to aforementioned characteristics is presented by simple bar charts. In addition to their application in describing the sample, descriptive statistical methods have been used to provide insight into research variables. For this purpose, three measures of central tendency (arithmetic mean, median and mode), as well as two measures of dispersion (standard deviation and interquartile range) have been calculated. Distribution of responses has also been presented by way of multiple bars. Considering that the responses were measured by ordinal scale, differences in evaluations and attitudes among individual groups have been analysed by means of nonparametric statistical tests. The Mann–Whitney test was used to test the significance of difference between two groups. The Kruskal–Wallis test was used to analyse differences between three or more groups. In cases where latter determined that there were at least two analysed groups with a significant difference, the Dunnin test was used for the purpose of their identification. It should be noted that empirical significance levels adjusted by Bonferroni correction are given alongside all Dunnin test results. Differences confirmed at a significance level below 5% were considered statistically significant for the purpose of this research. Statistical analysis of data was performed using statistical packages SPSS and Statistica, while graphical representations were generated using Microsoft Excel. Findings Two questionnaire surveys have been conducted for research purposes. A survey of attitudes of people who have gone on at least one religious journey or pilgrimage was conducted on a sample of 502 respondents, and a survey of attitudes and the level of involvement of local population in the management and application of sustainable tourism criteria in religious tourism destinations, as well as their level of satisfaction with the quality of living in the same observed religious destinations, was conducted by means of an online questionnaire, created using Google Forms, on a sample of 315 respondents. The survey was conducted in eleven selected religious destinations in the Republic of Croatia, namely: Ilača, Aljmaš, Slavonski Brod, Pleternica, Voćin, Ludbreg, Marija Bistrica, Krašić, Trsat, Sinj and Blato on the island of Korčula. The survey focused on the local population of a religious destination and on pilgrims, religious travellers and visitors of Croatian sanctuaries, keeping in mind the creation of a representative sample within the statistical dataset. The survey was conducted using a structured questionnaire in Croatian language. Statistical data analysis has been performed on questionnaires collected from pilgrims and religious travellers in religious tourism destinations and the results are presented in this paper. The results of conducted analyses of collected questionnaires show that the majority of residents of religious destinations have indicated a presence of unplanned tourism development within their destination and they predominantly agree with the assertion that unplanned tourism development has a negative impact on balanced economic and sustainable social development, which may lead to significant negative economic and social trends within their destination. It has been determined that local residents of religious destinations mostly agree that a synergetic effect of a religious destination's strategic management with the local community and higher-ranked church officials has an impact on the efficiency of strategic management, whereas pilgrims and religious travellers somewhat agree with this statement. The majority of residents who live in religious tourism destinations, including those involved in the hospitality and tourism industries, believe that religious tourism generates positive effects on their communality and agree that religious tourism benefits the development of their community in different ways. Almost 90% of respondents agree that tourism creates new job opportunities for the local population and contributes to youth employment, while over 90% of respondents agree that tourism has a significant impact on the town's aesthetics. Almost 88% of respondents agree that tourism increases sales of local products, thereby improving the quality of life of local residents through the development of events and infrastructure, while more than three quarters of respondents agree that tourism raises the level of environmental awareness and fosters conservation and renovation of cultural and sacral heritage. While local residents somewhat agreed with most assertions concerning the negative effects of tourism, such as that tourism effects an increase in the price of goods and services, causes an increase in number of seasonal workers, reduction in the number of permanently employed persons and precipitates an abundant production of waste, the majority of residents disagreed with the assertion that tourism development bears a negative impact on the development of other economic sectors. Survey respondents agreed with most of the statements evaluating the importance of factors which impact the defining of a tourism product of a religious tourism destination, such as statements concerning the spiritual significance of a religious destination (67%), the spiritual need of an individual worshipper (77%), and religious destination safety (64%), while only one factor was deemed irrelevant for the definition of a religious tourism destination’s tourism product by the majority of respondents (63%), namely the importance of the opportunity of travelling with pets. Pilgrims and religious travellers somewhat agreed with most of the claims regarding the impact of the parish community on the volume of tourists at a religious tourism destination, whereas they mostly agreed with the assertion that the proactivity of the parish priest and his ability to motivate parishioners significantly affects the number of pilgrimages and the number of pilgrims. Residents of a religious destination have indicated a lack of synergy among religious tourism stakeholders in the process of making decisions on the development of religious tourism and for the most part agree (84%) that successful tourism management of their destination requires strategic planning with the broader local community and involvement of all religious tourism stakeholders in tourism development decision-making, which is functionally tied to success in properly drawing up and implementing a sustainable strategic plan of development of the destination. In-depth interviews have also been conducted for the purpose of the doctoral dissertation. The interviews were formulated as semi-structured and were conducted with priests who manage church shrines at six religious destinations, namely: Aljmaš, Ilača, Voćin, Ludbreg, Marija Bistrica and Trsat. The second part of the research also involved in-depth interviews, but with directors of the tourist associations of the city of Rijeka, Vukovar-Srijem County, Marija Bistrica, Ludbreg, Osijek-Baranja County, and Sinj. In-depth interview contributors were selected for being the most competent representatives of their institutions, able to provide answers to questions posed within the scope of the subject being analysed, and for having the most practical experience in dealing with the aforementioned issues, thus they were the most relevant persons to provide answers. Upon analysing the responses obtained through in-depth interviews conducted with priests, church sanctuary managers and tourist association directors, one can conclude that all research questions have been answered, stating that religious tourism in Croatian destinations is not sufficiently valued, that insufficient attention is paid to ensure sustainable development of religious tourism in religious destinations and noting a lack of mutual cooperation between tourist associations and managers of sanctuaries, who are the key stakeholders of religious tourism in religious destinations. A proposal of a model for strategic management of a religious tourism destination is presented at the end of the paper. A vital part of the model involves the establishment of a strategic management structure for a religious destination which should certainly be unbiased and have executive power. Strategic management structure for a religious destination established in this manner should certainly be local enough to involve all key religious tourism stakeholders, such as representatives of local government, the church institution, the private sector, the local population, associations, pilgrims, religious travellers and tourists as key stakeholders of sustainable tourism development, encouraging them to cooperate in matters of sustainable tourist development of a religious destination. Such a structure should be strong enough and large enough so that its successfully established communication and coordination can determine a common development strategy and other instruments of religious tourist destination management which are founded on balanced principles of sustainable tourism development. Originality The scientific contribution of the doctoral dissertation is polysemantic. It can be viewed in the determination of certain economic rules, but also in the theoretical and applicative sense, which is evident in the presented results and conclusions of conducted research on selected religious destinations in the Republic of Croatia. In the theoretical sense, the contribution to the economic science is evident in the comprehensive and detailed overview of extensive, primarily foreign, scientific literature based on which key concepts pertaining to the topic of this paper have been systematized and defined. The analysis of reviewed scientific literature enabled the interpretation of important economic patterns, which emphasises the theoretical contribution of this paper. Unfortunately, domestic authors do not pursue the observed subject matter to a sufficient degree, and thus domestic literature dealing with the subject matter of this doctoral dissertation ‒ religious tourism ‒ is lacking, so this doctoral dissertation has at least partly filled the existing void in domestic scientific and technical literature. The paper's scientific contribution in the theoretical sense can be expressed through better understanding of the role and importance of sacral heritage and religious events on the successfulness of a religious tourism destination, as well as through cognitive facts resulting from research which can serve as a basis for defining models for religious tourism events founded on sacral heritage that can significantly impact the improvement of level of satisfaction of pilgrims, religious travellers, tourists and the local population with the ultimate goal of improvement of the economic impact on the religious destination, but also the economy as a whole. The theoretical impact is emphasised through the use of a valid and reliable measurement instrument (survey questionnaire and in-depth interview) used in the collection of primary data, so the scientific contribution is also emphasised through the applicability of statistical methods in the analysis of research data. Based on analyses of conducted research, by implementing the research results in its development strategies, planning and establishment of a religious and tourism events offering focusing on religion, culture, tradition and sacral heritage while ensuring sustainability, the management of a tourist destination can devise and implement models of religious and tourism events in accordance with the requirements of pilgrims, religious travellers, tourists and the religious destination itself. In the applicative sense of the scientific contribution, research results can aid the management and all stakeholders in religious destinations, serving as guidelines for strategic management, planning and implementation of tourism events based on religion, culture, tradition and sacral heritage, which will have a significant impact on the preservation of originality of culture, tradition and sacral heritage and its promotion on the tourism market, thus creating a unique religious tourism product and ensuring the recognisability of a religious destination. So with the approach of strategic management of a religious tourism destination, development of religious tourism going forward must be founded on criteria of sustainable development, i.e. on development of religious tourism which caters to the needs of attending pilgrims, religious travellers, tourists and the domestic population, satisfying economic, social, environmental and aesthetic requirements of the society, at the same time preserving religious and cultural identity and environmental processes, as well as resources of future development. Significant economic and non-economic effects will be achieved through sustainable development of the religious tourism offering and strategic management of a tourism destination.