As many as two million people were killed or persecuted by the former communist authorities in Romania, an official report says.
Soldiers joined the uprising against Ceausescu in 1989
The report was presented to parliament by Romanian President Traian Basescu. It was the first such official inquiry into Romania's communist-era crimes.
Mr Basescu said the 1945-1989 communist regime was "illegitimate and criminal".
He proposed a national memorial day and museum for the victims of communism, along with a new history textbook.
Mr Basescu was booed by the leader of the ultra-nationalist Greater Romania Party, Corneliu Vadim Tudor, and his MPs. Mr Tudor is named in the report as a "poet of the communist regime".
'Lies and terror'
The report was compiled by a presidential commission headed by Vladimir Tismaneanu, a well-known political scientist and former anti-communist dissident, who emigrated to the US in the 1980s.
Communist leader Nicolae Ceausescu was toppled and executed in a bloody uprising in December 1989.
Mr Basescu said the communist regime "trampled on the law and forced its citizens to live in lies and terror".
He levelled 21 charges against the communists, among them the imposition by force of a puppet pro-Soviet government in 1945, the destruction of Romania's democracy and persecution in the name of the class struggle of entire groups of Romania's population.
The report estimates the number of victims of communism in Romania at between 500,000 and two million.
It identifies former Romanian President Ion Iliescu - now an opposition Social Democratic Party senator - as one of the former close aides of Ceausescu and a prominent party bureaucrat who helped consolidate the communist regime.
Unlike most of its neighbours in Eastern Europe, Romania is only now addressing the injustices of the recent communist past.
Former Polish President and Solidarity leader Lech Walesa and Bulgaria's former President Zhelyu Zhelev were among those at the parliamentary session.