Regional policy is one of the oldest policies. Through its implementation, the state seeks to eliminate inequalities among certain parts of the country and to create conditions for their balanced development. The Republic of Croatia did not have a clearly defined regional policy until 2009 when the Regional Development Act, which seeks to resolve and address the issue of regional development throughout the state territory, was adopted. This Law, along with the Regional Development Strategy, is the basis of the regional policy of the Republic of Croatia. Due to large differences in the development of the region, it is necessary to stimulate the use of resources in less developed regions in order to achieve overall economic development. The significance of the regional policy was also influenced by becoming a member of the European Union. This can especially be recognized in terms of use of the funds that the Member States have the right to, efforts to bring Croatia closer to the average level of socioeconomic development in the European Union and ensuring sustainable development of local and regional self-government. Development index is an important indicator of the degree of development of units of local and regional self-government. Using this index, it is possible to establish and monitor the development of individual units of local and regional selfgovernment in relation to the state average.