[3] In a bull of 18 June 1081 Pope Gregory VII confirmed the extent of the territory of the diocese of Veroli for Bishop Albert.

[7] At some point during his reign, Pope Alexander determined that the number of Canons in the Cathedral of Saint Andrew in Veroli should be sixteen.

Finally, on 21 March 1921, Pope Benedict XV issued the bull "Sedis Apostolicae", removing Vallecorsa from the archdiocese of Gaeta and annexing it to the diocese of Veroli.

In central Lazio, Frosinone had long since become the largest city, as well as the regional capital and seat of magistrates and public services (from the early 19th century).

Pope Pius XII, therefore, authorized the Consistorial Congregation in the papal government to issue a decree, adding the name of Frosinone to that of the diocese of Veroli.

[16] The Second Vatican Council, in order to ensure that all Catholics received proper spiritual attention, decreed the reorganization of the diocesan structure of Italy and the consolidation of small and struggling dioceses, in particular those with financial and personnel problems.

Based on the revisions, a set of Normae was issued on 15 November 1984, which was accompanied in the next year, on 3 June 1985, by enabling legislation.