Two teenagers, age 15 and 14, were walking on a trail at Camp Cottermouth in Stromlo when they fell down the large embankment just after 5pm.

The fall left the 15-year-old trapped in the fork of a tree, suffering from back pain and minor cuts, while the other boy hurt his leg.

Emergency services were called via triple-0 about 5.10pm.

Firefighters and paramedics rushed to the scene, walking about 120 metres along the trail to reach the two boys.

The crews got back to the ambulance about 7.40pm, over two hours after the boys first fell.

Specialist rescue equipment was used to free the 15-year-old from the tree.

The boy was treated at the scene and taken to Canberra Hospital in a stable condition.

He was carried on a stretcher to an ambulance as a precaution for his back pain.

The other boy's leg injury was assessed but he did not require hospitalisation.

The rescue operation required three four-wheel-drives, sent by ACT Fire and Rescue and the ACT Ambulance Service, as well as an ambulance command vehicle.

Camp Cottermouth is the site of a Scouts camping ground, but it is unclear whether the boys were on a Scout trip at the time.