Terminal illness such as cancer can be cured by prayer, the head of the Catholic Church in Australia says.

But Catholic Archbishop of Sydney Cardinal George Pell admits such cures, like the miracle attributed to Mary MacKillop, is rare.

"Yes, obviously (cancer can be cured by prayer)," Cardinal Pell told ABC television today.

"And there are quite a number of examples in the books."

Cardinal Pell says that won't give sick people a false sense of security because they realise cure by prayer is a "very long shot".