The ban covers all South Eastern Sydney Illawarra Health premises including hospitals, community health centres and car parks.

Patients and visitors to Wollongong Hospital were left with no doubt about the directive as six signs of varying descriptions were placed at the Crown St entrance, a traditional hangout for smokers.

Health service chief executive Terry Clout said the move was intended to send a message that the organisation's priority was to protect people's health.

But not everyone was happy with the decision.

Patient Daryl Stansbury, who was in hospital for spinal surgery and had struggled downstairs in a back brace for a smoke, said the ban was the talk of the hospital.

He said a concern was that the move would force infirm smokers into the traffic on Crown St.

"There'll be mayhem. People are not going to stop smoking because of this. It will just push them across the street. There will be accidents because of it," he said.

He said a better solution would be to convert a section on the left side of the hospital entrance into a fenced-off smokers' area.

Fellow smoker Gary Smith, who was visiting a patient, said he understood why the ban was being enforced.

"I'm surprised that patients were allowed to come down and have a smoke in the first place," he said.

"It's not very nice when you see patients with a drip in their arm puffing away," he said.