The competitiveness of tourism and the effects of membership in the European Union on the business and competitiveness of Croatian tourism, applying the methods of quantitative analysis, is a topic that is dealt with through a doctoral thesis, with the aim of expanding scientific and applied knowledge on the analysis of the country's competitiveness as a tourist destination, placing the above in the broader context of the European of the Union. Competitiveness is an extremely complex and multidimensional concept that cannot be considered unambiguously in terms of the key factors that can provide such an advantage to a company or state. Different forms of competition and competitiveness (natural and economic, price and non-price, micro and macro level, national and international) are defined differently and have different meanings in a specific context. In relation to the approaches for the analysis of the competitiveness of the tourist destination, the doctoral thesis considers different models and concepts for the analysis of competitiveness, with the aim of defining econometric models in which macroeconomic variables related to the factors that determine competitiveness are selected, in the empirical part of the research. In accordance with the set problem and the subject of the research, the basic scientific hypothesis of the doctoral thesis (H0) was formulated, which reads: The accession of a country to full membership of the European Union has a statistically significantly positive effect on the competitiveness and business of tourism in that country, and the main effects of these processes are long-term. Since the basic research hypothesis contains several relatively independent relations between different variables, auxiliary hypotheses were also formulated: PH-1: The improvement of macroeconomic conditions and competitiveness factors of the national economy has a statistically significant and long-term positive effect on the competitiveness of tourism. PH-2: Economic growth in the member states of the European Union has a stimulating effect on the business results of Croatian tourism and its competitiveness. PH-3: The increase in foreign investments and economic growth in the member states of the European Union have a statistically significant and positive impact on the operations and competitiveness of tourism in full member states. Based on the set problem, subject and hypotheses of the doctoral thesis, the basic goal of the research was defined: Systematically investigate the competitiveness of Croatian tourism in the context of European Union tourism by applying quantitative methods of analysis and comparison of the results of the tourism business of other European Union countries, and based on the obtained results, define recommendations for the future. The special objectives of the doctoral work can be observed from a theoretical, empirical and applied point of view. The specific objectives of the theoretical part of the research are: ▪ defining the theoretical determinants of tourism destination competitiveness at the micro level and macro level ▪ upgrade and own interpretation of the model of competitiveness in tourism (goals, principles, factors, ...); ▪ analysis of tourism trends in the countries of the EU and globally; ▪ evaluation of the most commonly used (scientific) quantitative methods and techniques for the analysis of the competitiveness of tourism; ▪ application of the econometric approach in data analysis and making future assessments; ▪ synthesis of theoretical features and specifics of time series data modeling and panel data. The specific objectives of the empirical and applied part of the research are: ▪ quantitative and qualitative analysis of the current state of Croatian tourism with special reference to its key competitive advantages; ▪ quantitative analysis of the impact of tourism on the national economy of Croatia; ▪ application of selected quantitative methods for analyzing the competitiveness of Croatian tourism and comparing it with the competitiveness of selected EU countries; ▪ quantitative and qualitative analysis of the current state of EU tourism; ▪ determining the main impacts of EU membership on Croatian tourism today and tomorrow; ▪ highlighting the importance of the impact of EU strategic guidelines, policies and other measures by the European Commission on the tourism of EU member states; ▪ identifying the main goals and strategies of tourism development in Croatia; ▪ analyzing and interpreting the results of econometric research; ▪ formulating recommendations for increasing the competitiveness of Croatian tourism based on conclusions from empirical research. The theoretical part of the doctoral thesis serves the purpose of achieving the basic goal and special goals of the theoretical part of the research. The concept of competitiveness is considered, for a more detailed insight and a deeper understanding of its complexity, heterogeneity and actuality in today's time in which economic relations are strongly characterized by competitive relations between individuals, companies and states. The question of how to develop successful business models in conditions of constant uncertainty and global changes and how to build relationships that will primarily be based on cooperation and networking, and less on fierce competition, is also brought up to date. Partnerships can encourage innovation, the exchange of knowledge and resources, and the creation of synergies that will strengthen the competitiveness of Croatian tourism, as well as EU tourism. In order to delineate the fundamental determinants of the concept of competitiveness, a systematic review of the relevant literature identified a whole series of different factors from the micro and macro environment, which affect competitive abilities in different ways. Most authors are mainly focused on productivity, innovation, speed of adaptation, costs, processes, value for customers, strategies. In the context of the European Union, the notion and importance of strengthening competitiveness at the macro level is emphasized through all fundamental strategic documents (Lisbon Strategy, Europe 2020 Strategy, Next Generation EU). As part of the empirical part of the research, an analysis of the basic statistical indicators and business trends of Croatian tourism, as well as the tourism of other EU member states, was performed. By looking at the above indicators, which show the continuous growth of tourist traffic, its contribution to employment and the national economy in general through financial effects, it could be concluded that Croatian tourism is competitive, resistant to negative environmental influences and that it represents one of the rare segments in the national economy. an economy that can deal with international competitors on an equal footing. However, a deeper insight and analysis of the trend of other indicators, as well as a comparison of them with other EU countries, pointed to certain structural problems and limitations of Croatian tourism. These are reflected in the extremely unfavorable structure of the accommodation offer, in which family accommodation dominates with around 65%, followed by a relatively weak positioning in the competitiveness rankings in relation to comparable countries (according to the TTCI report for 2019, Croatia was positioned in 15th place out of 28 EU countries), extremely seasonally oriented business, excessive dependence of the national economy on tourism (the share of foreign exchange income from tourism in the total GDP is 18.9% in 2019), relatively low consumption by tourists, insufficient level of investments and weak business - investment climate. With the aim of consistency in the research and transparency in proving the basic and auxiliary hypotheses, through two dynamic models of panel data with independent variables, the impact of selected macroeconomic factors of competitiveness on the gross added value of tourism and related activities in the member states of the European Union was first examined, in a panel of 27 country for a 14-year time period (2006 to 2019), with 378 observations. Both models were used to test the auxiliary hypothesis PH-3. The "old" member states (EU-15) and the "new" member states (NMS-12) were analyzed separately. In the first model, for the "old" member states, it was shown that the variables of GDP change rate, inflation and exchange rate are statistically significant in the model (p < 0.05) with the expected signs in the regression coefficients, while the foreign investment variable was not significant. In the second model, for the "new" member states, the GDP change rate and inflation variables also show statistical significance (p<0.05), however, the exchange rate and foreign investment variables are not statistically significant in the model. It is concluded that the obtained results of the two models partially confirm the auxiliary hypothesis PH-3. Furthermore, an econometric analysis of the competitiveness of Croatian tourism was carried out through the evaluation of three separate models, which derive from auxiliary hypotheses PH-1 and PH-2. The empirical analysis included data for the period from the first quarter of 2001 to the first quarter of 2020, which resulted in a total of 77 observations. The goal was to model and analyze the determinants of business and competitiveness of Croatian tourism (approximated by the gross added value of tourism), and at the same time to include selected factors of competitiveness in the analysis. The variables foreign demand, investments in fixed capital, consumer price index and interest rates showed a statistically significant influence on the gross added value (p<0.05). Due to the importance of analyzing macroeconomic factors in the long term, the aforementioned required the application of more complex econometric methods, using vector autoregression (VAR model). The obtained results of all three mentioned econometric models support auxiliary hypotheses PH-1 and PH-2. Based on the analysis of the obtained results of the conducted quantitative research, it is concluded that the basic hypothesis of the doctoral thesis is fully accepted. Two auxiliary hypotheses (PH-1 and PH-2) fully support the basic hypothesis, while auxiliary hypothesis PH-3 partially supports it. Based on the indicators of the competitiveness analysis of Croatian tourism, strategic guidelines for the future development of Croatian tourism were formulated. It is concluded that tourism can represent a unique national economic cluster with which it is realistically possible to strengthen national competitiveness. In the era of globalization, new possibilities of technological development, sophisticated products, in the future it should strive to strengthen the offer of innovative, creative, recognizable tourist products with more added value, such as tourist products that offer a set of unique experiences related to the destination - natural beauty, culture, heritage, autochthonous local gastronomy, manifestations etc. It is also necessary to encourage the resident population, especially in continental part of Country, to actively participate in the development of sustainable tourism by starting entrepreneurial initiatives. As a member of the European Union, Croatia has at its disposal European non-refundable financial resources that can be an important lever in the realization of the previously mentioned activities. In the final part of the doctoral thesis, a conclusion is given in which the key results of the research are presented, as well as the literature, a list of pictures, tables and diagrams. The results of this research and the knowledge gained through it contribute to the improvement of theoretical achievements in the field of tourism competitiveness analysis and a better understanding of the effects of membership in the European Union in the field of tourism.