A New South Wales church volunteer has been jailed for 14 months for sex offences against children.

John Steggles, 70, pleaded guilty to a number of offences against children aged between seven and 14.

His crimes, which include committing and inciting acts of indecency, were committed between 1979 and 1991 when he was a volunteer bus driver and youth group leader for a Baptist church in Sydney's north.

The District Court in Sydney heard he often came into contact with children from disadvantaged backgrounds.

"A significant concern of mine... is that he used his position of significant authority over children he had selected as being vulnerable," Judge Robert Toner said.

But the judge also noted Steggles married in 2001 and has not engaged in criminal conduct since.

"I am mindful the man who now stands to be sentenced is somewhat different to the man who was somewhat isolated and sexually confused... when he committed these crimes," he said.

He sentenced Steggles to a fixed term of 14 months.

He will be released in November next year.