The patriarchal dioceses included Friuli, Carnia, Cadore, the southern part of Carinthia, the Carniola, and southern Styria in nowadays’ Slovenia.
The borders ran along the eastern bank of the Tagliamento, going down to include Claut and Erto, and then up to the hill of Colle St. Lucia; then they reached Lienz to the North and followed the right bank of the Drave to get to Ormoz, where they bent southwards along the rivers Solta and Kupa (Kolpa) and then turned westwards along the river Rinza on the Karst tableland; hence they reached the Adriatic Sea at Monrupino, including Monfalcone. Therefore the patriarchal diocese included Friuli, Carnia, Cadore, the southern part of Carinthia, the Carniola, and the southern Styria in the current Slovenia. From an ethnic viewpoint within its borders the patriarchal diocese gathered three different groups of people: the Italic, the Slavic (who were the majority since they occupied all the territory that nowadays corresponds with the Republic of Slovenia) and the German (the Alpine area of Sauris, the Gail valley in Carinthia and the territory of Villach).