Here follows a quick and brief overview of immigration policies in Italy as explained by the Ministry of Internal Affairs:

Policies aimed at promoting social cohesion, combating illegal immigration and easing regular immigrants’ reception and integration

Immigration policies are aimed at guaranteeing on the one hand law and order and internal security through the fight against illegal immigration and, on the other, the favoring of arrival and integration of immigrants who legally stay in our country.
Non-EU citizens may enter Italy if they hold a valid passport or equivalent travel document authorizing them to cross the border and an entry visa delivered by their country of origin, if required. 

Upon arrival in Italy, they must apply for a stay permit which, however, is not required if their stay in our country – for visits, business, tourism or study – is for periods not exceeding three months. 

EU citizens, in any circumstances, are not required to apply for a permit to stay in Italy.
According to law, foreign nationals having entered Italy without a regular entry visa are considered illegal immigrants, whereas foreigners who no longer meet requirements for staying in the national territory (e.g. expired permit of stay not renewed). 

The Italian Ministry of Interior not only deals with the handling of immigration flows into Italy but also with all initiatives for integration of foreigners aimed at creating an open society through a reception and integration progress.
For this specific purpose, the Ministry is implementing the ‘Solidarity and Management of Migration Flows’ programme co-financed by the EU.

Source: http://www.interno.gov.it/