The base for the analysis of population structure by nationality (by declaration) and language used at home, is the data from the National Population Census 2002. The author also refers to other scientists' study results, to justify assumptions used while disaggregating almost 775 thousand people (2% of total population) with unknown nationality or language used at home. The estimates and analysis results are widely compared with results of other studies, based also on special research. The results of the study show, that Poland, at the beginning of the XXI century, had a homogeneous population in respect of nationality and language used at home. Small national and language minorities (about 471 thousand persons, i.e. 1.2% of the total population, and 481 thousand i.e. 1.3%, after adjustments based on disaggregation of unknown nationality or language), exist mainly in the Opolskie and Slaskie voivodeships (Germans and Silesians) and in Podlaskie voivodeship (Byelorussians). Unique use of the Polish language at home was declared by about 97-98% of population, Polish together with a second language was used at home by 1,3% of population, and exclusively foreign languages - by only 0,14%. Among the foreign languages used at home, German and English were most frequently declared. Also, relatively frequently the Silesian and Kashubian dialects were used at home.