A man has been hit by a truck on Adelaide Street in Brisbane's CBD in what a witness said was an "absolutely disgusting" accident on Wednesday.

John Smith said he watched the man as he was "hit pretty hard" by the truck.

A man has been hit by a truck on Adelaide Street in Brisbane's CBD. Credit:Drew Creighton

"It was pretty scary, the poor fellow, he was still unconscious when they put him in the ambulance." Mr Smith said.

"He wasn't moving.