The article deals with main stages of the formation of secular state in Italy. These included: the period of existence of a multitude of Italian states (until 1870); the period of the “Vatican issue” (from 1870 to 1929); a period between 1929 and 1984, before the revision of the Lateran agreements; and from 1984 to the present. The elimination of the temporal power of the Pope first incited hatred of the majority of Catholics, but gradually, mostly due to the moderate policy of the Government, the relationship with the Church became less tense. The Lateran Treaty in 1929 created the Vatican City State and restored some of the earlier lost Church privileges. The real changes towards secularism became possible only since 1984, after the revision of the 1929 Lateran Concordat. Still, according to 1984 agreements, in spite of the principle of equality of all religions, the Catholic Church retains special treatment.