(By BBC News Online's Peter Gould)
The creation of new cardinals takes place about once every three years at a meeting with the pope known as a consistory, during which they receive the red hats that are the symbol of their rank.
Announcing the list last month, the Pope also revealed the names of two cardinals appointed in secret, three years ago.
This is a significant event because many of these new cardinals will one day be called on to take part in the conclave to elect the next pope, provided they are still under 80.
Their votes will not only change the mathematics of the election - the new pope could well emerge from their ranks.
It was Pope Paul VI who decreed that the over-80s could no longer vote in papal elections. He also said the number of cardinal electors should not exceed 120.
But each pope can re-write the rules, and while John Paul II has kept the age limit, he has decided to ignore the previous restriction on the size of the conclave.
In recent months, because of the number of cardinals turning 80, the number of electors fell to below 100. But after Wednesday's consistory, the total will rise to an unprecedented 135.
Given the frailty of the pope, who will be 81 in May, there is naturally speculation that this could be his last opportunity to create new cardinals and so influence the choice of his successor.
The stage is now set for the next conclave, and the scarlet-robed cardinals who gathered at the Vatican on Wednesday will be key players in the drama to come.
Among the new group of cardinals are some influential figures in the church, who could play an important role in the conclave, even if they do not become pope.
Giovanni Battista Re, a 67-year-old Italian, is prefect of the Congregation of Bishops, which enables him to advise the pope on episcopal appointments around the world.
After a successful career as a Vatican diplomat, with posts in Panama and Iran, he became deputy to the Secretary of State, giving him a key role as the pope's chief of staff.
Described as a workaholic, he is regarded as papabile - a possible pope.
Francois Xavier Nguyen Van Thuan was born in Hue, Vietnam, and was imprisoned by the Communist regime for 13 years, nine of them in solitary confinement. He is now president of the Pontifical Council for Justice and Peace.
Archbishop Claudio Hummes of Sao Paulo
Claudio Hummes, 66, is Archbishop of Sao Paulo in Brazil. He is seen as a moderate, and has spoken out on human rights issues.
The Polish-born Zenon Grocholewski has a top Vatican job as prefect of the Congregation for Catholic Education.
New cardinals from the United States include the Archbishop of New York, Edward Egan, and the Archbishop of Washington DC, Theodore McCarrick.
Cormac Murphy-O'Connor, Archbishop of Westminster
There is also a red hat for Cormac Murphy-O'Connor, the Archbishop of Westminster, and spiritual leader of the four million Catholics in England and Wales.
Also included is Karl Lehmann, the liberal-minded head of the German Bishops' Conference. He has been named as a cardinal despite concern at the Vatican over the involvement of the church in Germany in abortion counselling.
He caused consternation last year by suggesting that the pope would be prepared to resign if he became too ill to carry out his duties.
Choosing the next pope
It is the power to appoint cardinals that gives a pope the opportunity to influence the election that follows his death.
Because of John Paul's longevity, he has now appointed almost 93% of the electoral body. And a number of cardinals once thought of as future popes are now too old to stand any realistic chance of being elected.
Not surprisingly, most of those chosen by the pope to become cardinals share his traditional views on the teachings of the church.
So the next conclave is unlikely to elect a pope who is prepared to reconsider such controversial issues as contraception, priestly celibacy and the ordination of women.
But Father Thomas Reese, author of the book Inside the Vatican, says the next pope could still surprise the world.
"John Paul II has done exactly what you or I would do if we were elected pope. He has looked for people who agree with him on the most important issues," says Father Reese.
"But despite the fact that he has appointed all these people, there is no one like John Paul II - he is a unique person.
"Whoever is elected as the next pope is going to be quite different in terms of personality and style, and will respond to changing times and make changes in the church."
Perhaps the biggest question is whether the conclave will revert to tradition and elect an Italian pope. Before the election of the Polish-born John Paul II in 1978, Italy had held the papacy for more than 450 years.
In recent years, the number of Italian cardinals has steadily fallen. They now make up just under 18% of voters, a far cry from 1939 when they comprised more than half the conclave.
The numerical decline of the Italian bloc has coincided with the internationalisation of the College of Cardinals. Eastern Europe has increased its representation significantly.
The latter half of the 20th Century also saw the creation of many new cardinals from the developing world.
The latest appointments have reinforced their growing influence. Today the cardinals from Latin America make up no fewer than 20% of the voters.
Adding the cardinals from Africa, Asia and the South Pacific takes the figure up to 40%, a reflection of the vitality of Catholicism in these regions.
The latest appointments increase the number of cardinal-electors drawn from the Curia, the church's civil service. But Father Reese believes that the next pope is unlikely to come from their ranks.
"I think there are many bishops around the world who agree with John Paul II on his policies but have not really liked the way some of the Vatican bureaucrats have implemented them," he says.
"So I think there is going to be some backlash against the Curia, and I think the cardinals would first of all look for someone who has had experience as the bishop of a local diocese.
"I think they would be very reluctant to elect someone as pope who has been a Vatican bureaucrat all his life."
The changing composition of the College of Cardinals has led to speculation that the pope from Poland will be followed by a pope from the developing world. But Italy and the rest of Europe still provide almost half the cardinals under 80, among them some strong contenders.
So there is no clear favourite and the outcome of the election, whenever it takes place, is impossible to predict.
Indeed, some believe the record number of voters will make it harder to reach consensus.
The election will take place in a sealed-off area of the Vatican, well away from prying eyes, and will continue in conditions of the strictest secrecy until a new pope emerges, however long that takes.