The tapes were supplied by an international paedophile ring based in Russia, which takes orders via the internet from users around the world.
An international arrest warrant has been issued for a Russian man suspected of organising the ring.
Police have already filed criminal charges against more than 831 suspected users of child pornography in Italy.
They are trying to trace 660 other users in countries including Britain, the United States, Malaysia and Switzerland, who now risk detention on an international arrest warrant if they try to leave their county of origin.
Murder
The video cassettes show scenes of rape, torture and even murder of minors.
Customs police lured suspects by means of a fake website.
The software company Microsoft, and the FBI in the US, have been helping the Italian police.
The hunt involved a task force of 400 computer experts, including some hackers, to monitor the internet 24 hours a day, and identify people in many countries who order paedophile material online.
Software
The police set up a filter on the main Microsoft internet provider in Italy which warns any person seeking paedophile web sites that they are committing a crime and may be prosecuted under Italian law.
Police have been using advanced technology to bombard viruses at websites offering child pornography.
Through Interpol, the Italian police have asked the Russian police to re-arrest a Russian citizen who is believed to be in charge of the paedophile ring uncovered in Moscow.
This man has already been sentenced for distributing pornography, but was released from jail earlier this year, under an amnesty declared by the Russian parliament.