In the Holy Roman Empire, a bishop wore two hats: as a priest, he administered a diocese (German: Diözese), as a prince, he ruled a principality (his prince-bishopric, best rendered by the German word Hochstift, although Bistum and Fürstbistum were also confusedly used to denote indiscriminately the principality or the diocese). The map shows the HRE dioceses with each corresponding Hochstift circa 1780. Geographically, the bishop's diocese was always larger, sometimes considerably more so, than his Hochstift (i.e. Konstanz). As can be seen from the map, a bishop's Hochstift sometimes spilled over into a neighboring bishop's diocese. (J. Whaley, Germany and the Holy Roman Empire. Volume I, Oxford University Press, 2012, pp. 89–90)

All the Catholic bishops of the HRE were prince-bishops (Fürstbischof) and possessed a Hochstift and a seat at the Imperial Diet, with the exception of the bishops of Chiemsee, Gurk, Lavant and Seckau — the so-called Eigenbistümer — who were subordinate to the Archbishop of Salzburg, as well as the bishops of Breslau, Vienna, and the other bishops whose See lay inside the Habsburg hereditary lands (Austria, Bohemia, Silesia, Austrian Netherlands). While those bishops called themselves prince-bishops, they did not have a Hochstift or a seat at the Imperial Diet. They were therefore bishops in charge only of a diocese. (J. Whaley, Germany and the Holy Roman Empire. Volume I, Oxford University Press, 2012, pp. 89–90)

The prince-bishop of Strassburg (Strasbourg) lost effective control of his Hochstift on the west bank of the Rhine when Alsace fell under French rule in 1648. However, two small territories on the east bank survived under his temporal rule and he therefore remained a prince-bishop not only in name but in fact as well.

In 1667, an Apostolic Vicariate of Northern Missions (German: Apostolisches Vikariat des Nordens) was created to take care of the spiritual needs of the Catholic minorities that had survived in the areas of Northern and North-eastern Germany where some 15 dioceses/bishoprics had been abolished in the course of the Protestant Reformation. The other dioceses (those shown on the map) remained unchanged in theory but, in reality, some of them (i.e. Würzburg, Bamberg) had become almost entirely Protestant outside of the prince-bishop's own Hochstift.