A woman rock climber has suffered multiple serious injuries after plummeting down a 30 metre cliff in the Blue Mountains, west of Sydney.

The woman, aged in her 20s, is in a critical condition in hospital with injuries to her legs, chest, back and head.

She was believed to be rock climbing on Wednesday with a man in his 20s, who has suffered a serious leg injury.

"He is otherwise stable," said a spokesman for Ambulance NSW.

Paramedics called to the scene found the pair at the bottom of a 30m cliff at Mount Piddington in the village of Mount Victoria.

"They were at the bottom of this cliff in a difficult to access area," the spokesman told AAP.

Paramedics spent an hour treating the pair and the woman was winched out about 3.20pm (AEDT).

She has been taken to Westmead Hospital in a critical condition.

The man was winched out shortly after 4pm and was taken to the same hospital.