The topic of the paper is modeling tourism development in the function of planning. To this end, the work begins with the theoretical determinants of tourism system management, management functions, the goals of complex systems such as tourism. Then the importance and role of planning in tourism. Planning as the first and most important function of management helps to achieve goals and implements actions to achieve them. Planning as a function of management derives from the characteristic features of modern business, the effect of globalization, competitiveness and the uncertainty of the environment. Then, forecasting methods in the function of tourist planning are theoretically explained. The forecasting of the quantitative models applied in the paper is analyzed. These are naive models, smoothing models and multiple linear regression models. Based on the research, it is concluded that the naive model II, the model of linear moving averages, is the most accurate because the forecasts of these models have the smallest deviations from the actual number of realized overnight stays. In the model of multiple regression, the independent variables have a great influence on the dependent one (BDP, unemployment rate, consumer price index), which is reflected in the large numbers of declines in the number of overnight stays in Dubrovnik if the independent variables in the emitting markets of the United Kingdom, USA and Germany increase by only 1%. The City of Dubrovnik should pay special attention to monitoring these indicators in emitting markets in order to be able to change and adjust its tourist offers, is to influence the price and become more competitive in the tourist market so as not to reduce the number of overnight stays. Pay special attention to strategy development, is actions taken in these situations. In future research, it is recommended to conduct detailed research of strategic documents, complementarity of set goals in strategies and implemented activities, survey of local population on satisfaction with implemented projects and equal representation of all three components of sustainability in development documents and their implementation planning.