San Silvestro in Capite
Dietrichstein was ordained in 1597 and then elevated to cardinal only two years later, in 1599, with an appointment as cardinal-priest of San Silvestro in Capite. In May of that same year he was elected as Archbishop of Olomouc, though his election was opposed by members of the local cathedral chapter. He was consecrated by the pope himself, with special dispensation for having not reached canonical age (he was only 29 at the time). According to historian Ludwig von Pastor, Dietrichstein became the, "soul of all Catholic undertakings in Moravia". It was apparently due to Dietrichstein's zeal that protestant reformer Karl von Zierotin was forced into early retirement.