Police believe a man found unconscious in Sydney's CBD was punched in the side of the head in an unprovoked attack as he was walking along the street.


The 33-year-old was found unconscious on George Street at 12.30am (AEST) on Sunday by paramedics called to the scene.


He's being treated at St Vincent's Hospital for head and possible neck injuries.


It's the latest in a series of apparently random bashings in Sydney.


Thomas Kelly, 18, died in July last year after he was punched to the ground while walking in the Kings Cross nightclub district and last month a 26-year-old was bashed in Sydney's north after refusing a stranger's request for a cigarette.


Also in June, 26-year-old Simon Cramp was left fighting for his life after allegedly being king-hit in Sydney's CBD.


Police believe the latest victim was attacked while walking down George Street, and have appealed for anyone with information to come forward.


Police and members of the man's family will address the media on Sunday.


AAP