Tourism is a complex system representing a complex phenomenon in modern society and it is characterised by a large number of organisational participants within the national, economic, social and professional organisational structure. An adequately defined organisational structure is required in order for the system to function efficiently. The aim of this paper is to indicate the complexity of the organisational structure of tourism in the Republic of Croatia and the European Union countries, to make a comparison and to determine the significance of various organisational structures to ensure efficiency of all processes in tourism. The topic of the paper is organisation of tourism in the Republic of Croatia and the EU countries. The beginnings and the reasons for development of tourist organisations, the emergence of receptive and emissive organisations as well as the tourism system are analysed. The method of comparison was used to analyse the organisational structures of tourism in the Republic of Croatia and the EU countries and on those basis physical and financial tourism indicators were analysed in order to determine whether there is a link between the organisational structure complexity and results achieved in tourism. Research methods of analysis, synthesis, induction, deduction and statistical methods were used to test the set hypotheses. It has been found that although the Republic of Croatia has relatively good results in tourism, there are still the issues such as the high share of tourism in GDP, seasonality, large administrative burden – a large number of local municipalities in relation to the area and population, as well as mass tourism that is in conflict with the policy of sustainable development that the Ministry of Tourism and Sports has been trying to implement as part of their tourism development strategy.