Purpose – The impact of tourism is an ongoing research interest among scholars as it is directly related to the tourism development process. Residents’ perceptions of tourism impacts can indicate development guidelines if planners pay attention to them. Design – We examine residents’ perceptions of tourism impacts and their support for sustainable tourism development in two similar tourism destinations, Portorož and Opatija, based on their similarity, closeness, and connectedness through time to the present. Approach – There is an urgent need for a strategic development change for both destinations, which are coping with typical negative impacts of tourism, including seasonality, noise and, overcrowding. Methodology – Four hundred and forty-six residents surveyed indicated that tourism development is an important issue. Two databases were combined in order to conduct inference data analysis using SPSS 21 statistical software. Depending on the type of variables, t-test and ANOVA were used for the analysis in addition to the descriptive statistics. Findings – Residents point out a clear and strong message for the importance of their inclusion and active involvement in the decision-making processes of sustainable tourism development. Furthermore, our results revealed higher criticism of tourism impacts among those personally involved in tourism (employed or economically dependent on tourism) and among Portorož locals. Originality - We provide theoretical and practical implications of the research, especially suitable for planners of the destination development, who should be cautious about residents’ reaction to tourism at the destination.