Former Vatican treasurer Cardinal George Pell was sentenced to six years in jail on Wednesday for sexually abusing two choir boys in Melbourne in the 1990s, and will be registered as a sex offender for the rest of his life.

County Court of Victoria Chief Judge Peter Kidd, who handed down the sentence in a live television broadcast, said there was a real possibility that at age 77, Pell could spend the rest of his life in prison.

Pell, a former top adviser to Pope Francis, is the most senior Catholic to be convicted for child sex offences.

His downfall gets to the heart of the papal administration a scandal over clerical abuse that has ravaged the Church's credibility in the United States, Chile, Australia and elsewhere over the last three decades.

"In my view, your conduct was permeated by staggering arrogance," said Kidd in handing down the sentence after Pell was convicted of five charges of sexually abusing two children.

"Viewed overall, I consider your moral culpability across both episodes to be high," he told the packed court room.

Pell, who appeared in court without a priest's collar for the first time during the case, showed no emotion during the sentencing hearing that ran for more than one hour. He has maintained his innocence and has filed an appeal that is scheduled to be heard in June.