The population of Lithuania (2001 estimate) is 3,610,535, giving it a population density of 55 persons per sq km (143 persons per sq mi). Lithuania is highly urbanized, with 74 percent of the population living in urban areas. Unlike most other republics of the former USSR, the country is not dominated by a single urban center. Vilnius, the capital, is the largest city, followed by Kaunas, an industrial and commercial center, and Klaipeda, an important seaport.

Ethnically, about 80 percent of the population is Lithuanian, but there are also Russians and Poles and lesser numbers of Belorussians, Ukrainians, Jews, Latvians, Tatars, Gypsies, and others. Natural increase, rather than immigration, has accounted for most of the recent population growth. This situation distinguishes Lithuania from its Baltic neighbours. The comparatively high level of ethnic homogeneity in Lithuania and the persistence of Roman Catholicism in the face of decades of Soviet promulgation of atheism as the official state ideology further distinguish Lithuania from Latvia and Estonia, where historically German-Scandinavian religious and cultural values have predominated.