On the death of Cardinal Giovanni Colonna on 26 September 1508, Pompeo was named bishop of Rieti by Pope Julius II on 6 October 1508; he ruled the diocese until he resigned in 1520 in favor of his nephew, Scipione Colonna.
Pompeo was named bishop of Rieti by Pope Julius II on 6 October 1508. This was on the death of Cardinal Giovanni Colonna on 26 September 1508. He ruled the diocese. He resigned in 1520 in favor of his nephew. Scipione Colonna was his nephew.