Religion and Carpatho-Russian/Rusyn history are deeply intertwined, often resulting in controversy. Carpatho-Russians were originally of the Orthodox faith (though even this is controversial as some claim there was Catholic influence from Moravia). In fact, one of the earliest saints of the Monastery of the Caves at Kiev was the Carpatho-Russian Moses Uhrin (died 1043)¹, who prior to becoming a monk served Boris, the prince of Ancient Rus'. Moses and his brothers’ Efrem and Georgii stories are recorded in the famous ‘Russian Primary Chronicle’. Also originating from this time is the unique Carpathian church prostopinije (Plain Chant), which is closely related to the ancient chant of Kievan Rus' and has even preserved elements of it.²

www.simkovich.org/religion.htm