John, a bishop of Cattaro, was certainly mentioned in the acts of the Second Council of Nicaea in 787. John was also mentioned in 809 in epigraphical inscriptions found in Cattaro. Bishops of Cattaro were mentioned in Ecclesiastical Assembly of Spalatum in 925 and 928, during the reign of King Tomislav. Only a fragmental list of the bishops before the 11th century were preserved. Afterward, since 1090 till the present day, a complete list has existed, beginning with bishop Grimoald, of Lombard origin.