According to article 34, paragraph 1 of the Constitution of April 2, 1997, Polish citizenship is acquired at birth if at least one of the parents already possesses citizenship (ius sanguinis). Naturalisation is possible after a minimum of five years of legal residency in Poland. Although it is not stipulated in national law, multiple citizenships are tolerated in practice.
Between 2002 and 2005, 7 623 people were naturalised. Some 2 866 people were naturalised in 2005 alone, a considerable increase compared with the previous year (2004: 1 937 naturalisations). This increase can be attributed primarily to the processing of a backlog of applications. Most of the people who were naturalised in the period between 2002 and 2005 came from Ukraine, Belarus, the Russian Federation, Israel, Lithuania and Germany.