Emergency crews were called to Hunter River Reserve at Greta just before 4pm on Tuesday, after the teenager had fallen.

One paramedic road crew, two Ambulance Rescue Paramedics, a NSW Ambulance Inspector and the Westpac Rescue Helicopter with a Critical Care doctor and a Critical Care paramedic on board were dispatched to the scene.

The boy had fallen about 15 metres before becoming tangled in a tree.

As night fell, two Ambulance Rescue paramedics and the Critical Care paramedic roped down to the patient, who had suffered a broken leg.

A Critical Care doctor was also lowered to the patient, who was secured and stabilised while further specialist resources were mobilised for his extrication.

The teenager was brought to the top of the cliff on a Stokes litter just before 7pm and was taken to John Hunter Hospital in a stable condition.

"The patient was in an extremely precarious position a number of metres from the bottom of the cliff," Inspector Joel De'Zuna said.

"What was already a difficult and complex vertical rescue, became even more difficult as we lost the daylight and it started to rain.

"This was an amazing multi-agency response which saw paramedics working alongside Fire and Rescue NSW, NSW Police, members from VRA Rescue NSW and Rural Fire Service crews.

"I can't praise highly enough the way our Ambulance Rescue Paramedics and Critical Care team put their rescue training into practice in getting down to this patient, securing and stabilising him, and taking him up the cliff to safety."

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