Pope Francis was formally installed as bishop of Rome on Sunday and he urged lapsed Catholics not to be afraid to return to God.
Francis celebrated a Mass before thousands of people in the Rome Basilica of St. John in Lateran to formally take possession of the cathedral in his capacity as bishop of the Italian capital, his other major role along with the papacy.
Francis, the former archbishop of Buenos Aires, has indicated that he intends to embrace his role as Rome's bishop as well as leader of the 1.2-billion-member Catholic Church.
Since his election on March 13, he has referred to himself more often as "bishop" than "pope" and is expected to visit many of Rome's parishes, a practice he maintained in Buenos Aires.
In his homily in St. John's, whose adjoining palace was the residence of most popes until the 14th century, Francis urged Catholics who had strayed from their Church to have the courage to return.
"God's patience has to call forth in us the courage to return to him, however many mistakes and sins there may be in our life," he said, speaking in Italian.
Francis has inherited a Church weakened by sexual abuse of children by priests in many countries and allegations of corruption in the Vatican.
Many have said their faith was shaken by the scandals. Francis, who is expected to make new appointments to clean up the Vatican's often dysfunctional bureaucracy, urged Catholics to let God back into their lives.
"We hear many offers from the world around us; but let us take up God's offer instead: his is a caress of love. For God, we are not numbers, we are important, indeed we are the most important thing to him; even if we are sinners, we are what is closest to his heart," he said.
Thousands of people who could not get into the packed basilica gave Francis a rousing welcome outside as he rode around a large square in an open jeep.
They applauded as he unveiled a plaque re-naming part of the square after Pope John Paul II, who died in 2005.