This paper approaches some of the characteristics of the regional development of Serbia, from the perspective of two models of territorial organization: one is governmental (administrative and statistical), and the other is functional. The imbalances in the levels of development of various territorial units of Serbia (regional disproportions) are the consequence of many structural disharmonies, material limitations, and problems with population structure, during many years, all worsened by political and economic events at the end of the twentieth century. Also, in this paper we point out the main characteristics of undeveloped regions, the criteria with which we can define them, and a typology of the municipalities inside each such region.