ENThe paper discusses Polish as a religious language in Eastern Europe, particularly in Lithuania, and – to a lesser extent – Belarus and Ukraine. The author focuses on language changes within the sphere of religion concerning the use of Polish and other languages in the Roman Catholic Church. The process of depolonizing the Roman Catholic Church along with its Belarusization in Belarus and Ukrainization in Ukraine has been observable. Moreover, the article overviews the response of the Church members to the eradication of Polish as a religious language and replacing it with Belarussian and Ukrainian. With respect to Lithuania, the analysis based on field research (informants) depicts the current situation of the Polish language as its usage has come to be limited and as it has begun to be eradicated from the Church in two Polish-speaking enclave communities that are disintegrated today (the Kaunas region and the Zarasai region).