City ranking has become a central instrument for assessing the attractiveness of urban regions by which cities are assessed and ranked according to different economic, social and environmental characteristics. As a basis for developing a model for assessing the effectiveness of smart cities in the Republic of Croatia in the context of smart urban units, in this doctoral thesis 38 indicators were used described in the norm ISO 37120 - indicators for urban services and quality of life, norm ISO 37122 - sustainable cities and communities, indicators for smart cities and additional indicators that are distributed in six dimensions of a smart city, namely: smart economy, smart governance, smart citizens, smart environment, smart living and smart mobility (Giffinger et al., 2007). In creating a model for assessing the efficiency of smart Croatian cities, three separate analyzes were conducted. In the first part, 127 Croatian cities are ranked according to 38 indicators of the stated norms according to six dimensions of the smart city, using the methodology of equal weights, and the result is the index of smart Croatian cities which is constructed as an average of all indicators of each dimension, and which represents the basis for ranking smart Croatian cities. This methodology has enabled an effective comparison between all dimensions and all cities, proving that it is applicable to all cities in the country regardless of their size. In the second part, an efficiency analysis is performed, ie ranking of cities using Data Envelopment Analysis (DEA) in which weighting is derived from the data themselves, ie the factors of relative efficiency of 127 Croatian cities are identified and quantified in order to identify and eliminate sources of inefficiency in cities that are marked as relatively inefficient, according to exemplary cities. The inputs were represented by indices of six dimensions of smart cities, and the output is represented by the development index of each city. In the third part, in order to determine the stability of the rank, a comparative analysis of the rank results of the two methodologies was performed and it was determined that the best ranked cities are Dubrovnik, Rijeka, Pazin, Split, Korcula, and the worst ranked cities are Kutina, Glina, Komiza, Bakar, Petrinja and Skradin. The last part of the dissertation was followed by the interpretation and graphical visualization of the results through a business intelligence software.