The agency says youth courts, which handle cases involving 12 to 17 year-olds, completed about 48,000 cases in 2011-2012, down 10 per cent from the previous year.
It was the third straight year of decline for youth cases and the lowest number of cases completed in youth courts since national data were first collected in 1991-1992.
The largest drop in completed adult cases was the 17 per cent reported in the Northwest Territories, with cases in Prince Edward Island down 13 per cent.
Newfoundland and Labrador reported the only increase in 2011-2012, with cases up 2.0 per cent, while Quebec remained stable.
The largest decreases in the number of completed youth court cases were in the territories, where declines ranged from 23 per cent to 36 per cent, while British Columbia recorded the largest provincial decline, at 16 per cent.