Pope Benedict will install his first group of new cardinals today.
Twelve of the 15 men are under 80 and so are eligible to enter a conclave to choose a pope.
They are mostly from Europe, Asia and the United States, including the Irish-American Archbishop of Boston,
rather than the Latin American and African regions - often seen as key to the 1.1-billion-strong Church's future.
Archbishop Sean O'Malley, who took over in Boston in 2003 to clean up after a clerical sexual abuse scandal forced Cardinal Bernard Law to resign, will be the second American receiving his red cardinal's hat at a ceremony in St Peter's Square.
The best-known face will be Krakow Archbishop Stanislaw Dziwicz (66), who was at the late Pope John Paul's side during 26 years as his private secretary and is one of the most influential men in the Vatican.
The most senior will be William Levada (69), the former archbishop of San Francisco who shot to prominence last May when Pope Benedict unexpectedly appointed him to take his place as head of the Vatican's powerful doctrinal department.
Politically, the most interesting is Hong Kong's Bishop Joseph Zen Ze-kiun, an outspoken supporter of democracy and critic of Beijing's restrictive religious policies.
After today's ceremony, known as a consistory, the church will have 193 cardinals, 120 of them under 80.