The total population of Croatia at the time of the 1991 census was 4,784,265; a 2001 estimate was 4,334,142. During and after the war ethnic Serbs fled Croatia while ethnic Croats moved in. Although Croatia’s natural population growth rate, which measures births and deaths, was negative in 1998, the actual population grew by 1.48 percent due to immigration. Life expectancy at birth was 74 years in 2001. The population density in 2001 was 77 persons per sq km (199 per sq mi). In 1999, 57 percent of the population was urban. Most of the urban population is concentrated in four cities: Zagreb, the country’s capital and primary industrial center; Split, a seaport; Rijeka, also a seaport; and the agricultural and industrial center of Osijek.

While most of Croatia's Serbs live in urban centres, just over one-quarter are scattered in villages and towns, mostly in lightly populated parts of the central mountain belt, in Lika and Banija, and in northern Dalmatia. There is also a smaller concentration in Slavonia. Many of the Serbs in Croatia are descendants of people who migrated to the border areas of the Austrian empire between the 16th and 18th centuries, following the Ottoman conquest of Serbia and Bosnia. Their original role as frontiersmen against Ottoman incursions, in addition to their poverty and geographic isolation, ensured that Croatia's Serbs would remain among the least-educated and often better-armed and more violence-prone residents of the region.