© AFP.The Vatican's UN Ambassador, Monsignor Silvano Tomasi (L), and former Vatican Chief Prosecutor of Clerical Sexual Abuse Charles Scicluna are at the hearing.
The Church was asked why it continued to describe such abuse as an offense against morals rather than a crime against children.
Archbishop Silvano Tomasi said such crimes could "never be justified" and every child should be "inviolable".
The Vatican earlier refused a request for data on abuse.
When it argued that such cases should be heard in the countries where they took place, it was accused of responding inadequately to abuse allegations.
This is the first time the Holy See is defending itself in public over its record on sex abuse.
Victims say they hope the hearing, which is being broadcast live, will prompt the Church to end its "secrecy".
Pope Francis announced last month that a Vatican committee would be set up to fight sexual abuse of children in the Church and offer help to victims. He also broadened the definition of crimes against minors to include sexual abuse of children.
The Holy See is a signatory to the UN Convention on the Rights of the Child, a legally binding instrument which commits it to protecting and nurturing the most vulnerable in society.
'Inviolable'
It was, Archbishop Tomasi said in his opening statement, important to establish the truth of what had happened in the past, to prevent it ever happening again, to see justice done and to provide healing for the victims.
The Vatican, he told the panel, would welcome any suggestions from the UN's Committee on the Rights of the Child (CRC) to implement its obligations.
CRC members then set out their questions, asking about the Church's practice of moving priests suspected of abuse and allegations that it had concealed such abuse.
"Does the Holy See believe that paedophilia is something that can be successfully overcome?" was one question.
How, the Vatican was asked, did it go about training priests for work with children? What oversight was in place for Catholic institutions such as schools, and what plans did it have to collect data on child sex abuse?
Last July, the CRC requested detailed information about the particulars of all sexual abuse cases notified to the Vatican since 1995.
The questions included whether priests, nuns and monks guilty of sexual crime were allowed to remain in contact with children, what legal action had been taken against them, and whether complainants were silenced.
In its response, the Holy See said it was not its practice to disclose information about the religious discipline of clergy unless specifically requested to by the authorities in the country where they were serving.
It stressed that it had changed the criteria for choosing priests and revised Church law to ensure clergy were properly disciplined.
It also insisted that as a diplomatic entity it was "separate and distinct" from the Roman Catholic Church.
This was dismissed as a false distinction by critics like Britain's National Secular Society, which said the Holy See operated a "firm command and control structure over the worldwide Church".
'We request justice'
© AP.Teodoro Pulvirenti now lives in New York.
Mr Pulvirenti, who now lives in the US, told the Associated Press it was time for the Vatican to end its "secrecy" over a global sex abuse scandal.
He recalled how he had gone to the priest for guidance as a teenager.
"I went to his office and... something strange happened and he started putting his hands under my T-shirt and that's when the abuse actually started," he said.
He moved to America in 2006 but returned to Sicily in 2011 and confronted the priest, Don Carlo Chiarenza, who was subsequently found guilty by the Vatican and dismissed from his diocese. The decision is currently under appeal.
"I'm not coming out against the Vatican and I don't want the Church to think the victims are against the Church, against the Vatican," Mr Pulvirenti said. "We are standing up for our own survival, but we request justice."
Catholic Church abuse scandals
- Germany - A priest, named only as Andreas L, admitted in 2012 to 280 counts of sexual abuse involving three boys over a decade
- United States - Revelations about abuses in the 1990s by two Boston priests, Paul Shanley and John Geoghan, caused public outrage
- Belgium - The bishop of Bruges, Roger Vangheluwe, resigned in April 2010 after admitting that he had sexually abused a boy for years
- Italy - The Catholic Church in Italy admitted in 2010 that about 100 cases of paedophile priests had been reported over 10 years
- Ireland - A report in 2009 found that sexual and psychological abuse was "endemic" in Catholic-run industrial schools and orphanages for most of the 20th century
I've wondered if the priests indulging in this were excomunicated??