Two men have been hospitalised, one with serious head injuries, after a single car crash in North Canterbury today.

The crash happened about 6.50am on Onepunga Road, near Broomfield, about 50km north of Christchurch.

A man in his 40s suffered serious head injuries and was flown by Westpac rescue helicopter to Christchurch hospital, a St John Ambulance spokesman said.

Another man in his 50s suffered moderate injuries.