1988 census Poland had a population of 37,878,641. The 2001 estimate was 38,633,912, yielding an average population density of 124 persons per sq km (320 per sq mi). Poland’s highest population densities are in the southern upland areas; the lowest densities are in the northwest and northeast. The average annual rate of population growth was very high in the period following World War II, but after the 1960s it declined to less than 1 percent, and in 1997 the population was estimated to be decreasing. Reasons for the decline include high unemployment and increases in the cost of child rearing. The rate of urbanization in Poland has accelerated since the end of World War II.

Before World War II the Polish lands were noted for the richness and variety of their ethnic communities. In the provinces of Silesia, Pomerania, and Masuria (then in Germany) there was a significant minority of Germans. In the southeast, Ukrainian settlements predominated in the regions east of Chelm and in the Carpathians east of Nowy Sacz. In all the towns and cities there were large concentrations of Yiddish-speaking Jews. The Polish ethnographic area stretched eastward: in Lithuania, Belarus, and western Ukraine, all of which had a mixed population, Poles predominated not only in the cities but also in numerous rural districts.