When a Pope dies the Catholic Church's most important priests, called Cardinals, all travel to Rome. One of them will be the new leader.
They go to the old Pope's funeral and then after nine days they start to elect a new Pope.
The voting is very secretive and there are lots of odd traditions.
- Each Cardinal gets one vote.
- The new Pope must get over two thirds of the votes.
If after a week the Cardinals still have not picked a new Pope, then they can choose someone who only has half of the votes.
The results are sent to people outside the Vatican using smoke signals.
- Black smoke means the Cardinals haven't made up their minds yet.
- White smoke means they have chosen a new Pope.