The aim of this thesis is to analyze the economic potentials of two counties, Istarska county and Požeško-slavonska county, primarily by applying a comparative method, but also other methods: analysis and secondary research, historical, statistical and compilation methods (acquisition of other people's knowledge). It starts with general assumptions about Croatian counties, demographic issues, as well as issues related to regional development of the Croatian and regional policy of the European Union as a tool for developing their own development potentials. The central part of the thesis analyzes the comparative advantages, the economy and the strategic priorities of the Istarska county and Požeško-slavonska county. The research problem relates to the question of how to put the untapped potential into full use for economic development in the two counties observed, and in particular in the Požeško-slavonska county as one of the least developed Croatian counties. The basic conclusion is that there are large differences in economic development between Istarska county and Požeško-slavonska county, primarily according to the average achieved economic development.