In the 16th century, Orthodox believers predominated in the Ruthenian regions of the Grand Duchy of Lithuania, yet in addition to the organisational structure of the Orthodox Church there was also the Catholic Church structure. This article seeks to investigate how the officials of these two Churches coexisted in the Ruthenian lands of Polotsk and Vitebsk in the 16th century. In the Appendix, which is at the end of the article, five documents are published that are kept in the Manuscripts Department of the Wroblewski Library of the Lithuanian Academy of Sciences that considerably contribute to existing knowledge about the researched topic.