The Ruthenian Catholic Church is a sui iuris (i.e., self-governing) Eastern Catholic Church (see particular Church), which uses the Divine Liturgy of the Constantinopolitan Byzantine Eastern Rite. Its roots are among the Rusyns who lived in the region called Carpathian Ruthenia, in and around the Carpathian Mountains. This is the area where the borders of present-day Hungary, Slovakia and Ukraine meet. The Ruthenian Catholic Church is in full communion with the Bishop of Rome who is spiritual leader of the 23 sui iuris particular churches which compose the Catholic Church.