A former volunteer bus driver involved in a church youth group has been charged with molesting young Sydney children over three decades.

The man, now aged 69, was arrested at Bilpin, near Windsor in Sydney's north-west, at 8.15am today, police said.

It followed allegations he sexually molested and assaulted young children during the 1970s, '80s and '90s.

Investigations were sparked after two men and two women made statements to police, North Shore crime manager Detective Inspector Peter Yeomans said.

"These four people have made statements alleging acts of sexual and indecent assaults upon them between 1978 and 1992," he said in a statement.