The Observants’ Ruthenian Province was established in Lvov in 1637, as a result of the chapter authorities’ decision. Its twilight was the year 1772. The present article shows the Province’s internal organization, i.e. its offices, chapters, studies, inner life and social activity. All issues presented here ensure the readers of the Province’s great vitality. The activities undertaken by the monks, prove that they played a significant role in the development and reinforcement of the Catholic Church on the eastern frontiers of Poland.