Calvary Public Hospital in Canberra declined to comment on the matter but said the death had been referred to the Coroner.

Witness Jenny, who requested her last name be withheld, said she was in the hospital's emergency department waiting room with her son on Monday night about 9.45pm when the man's death was discovered.

Jenny had been waiting for about five hours with the man believed to have been in the waiting room for a number of hours.

Jenny estimated the man who died to be in his 40s and said he was alone at the hospital.

Jenny said the man was discovered when a woman sitting next to him - also waiting to be seen - realised he was slumped over and unresponsive.

Previously he had appeared delirious and talking to himself.

"She just screamed 'quick, press the buzzer, he needs help'," Jenny said.

A code team arrived and performed CPR on the man who appeared to be already dead.

The man was eventually moved into the emergency department away from the waiting room.

Shocked members of the public in the waiting room were left to digest what had happened, with blood remaining on the floor.

"This poor man died in a chair," Jenny said. "Everyone was just shocked, it was so distressing.

"I'm still having flashbacks and I used to be a nurse."

Jenny said there were a number of children in the busy waiting room and no explanation or support was given to people after the incident.

"People need to know something like this can happen," she said. "People go to hospital thinking they're safe and then this man dies waiting.

"Maybe needs to be an inquiry of some sort.

"It's just shocking that something like this could happen."

A Calvary spokesman was unable to comment on the details of the case or whether the man's family had been informed about the specifics of his death.

“The death of a person on New Year’s Eve in the Calvary Emergency Department has been referred to the coroner," he said.

"Calvary is not able to provide any comment at this time.”