A 53-year-old man has died two days after a daylight fight in Brisbane's CBD that shocked bystanders.

Emergency services were called to Adelaide Street camera store digiDirectBrisbane about 10.40am on Monday after reports of a fight outside.

Police speak to a man after the fight in Adelaide Street.

The 53-year-old scuffled with a 55-year-old man from West End, then sat on a nearby bench before losing consciousness.

He was treated at the scene by paramedics who described the patient as suffering from a "medical episode".