CBC's French-language service has identified the injured man as Giuseppe Fetta, a known thug with a criminal past and ties to organized crime.
Montreal police were called to the scene of the shooting on St-Laurent Boulevard between Fleury Street and Sauriol Street at 10:10 a.m.
Fetta was rushed to hospital with gunshot wounds to his chest and legs.
The suspect fled the scene before police arrived.
St-Laurent Boulevard remains closed between Sauriol Street and Fleury Street, as the police investigation continues.
Rounded up in Operation Coliseum
Fetta was arrested as part of Operation Coliseum, a major police crackdown in 2006 that rounded up more than 100 alleged Mafia members.
Fetta pleaded guilty to a charge of weapons possession and was released in 2008.
Another man in his 40s was shot to death on Nov. 15, on the same block of Boulevard St-Laurent where Fetta was injured. It is not known if the two incidents are related.
Fetta's shooting is the latest in a rash of murders and attempted murders that have happened in and around Montreal in the weeks since Montreal's Sicilian Mob boss, Vito Rizzuto, was released from prison in the United States on Oct. 5. Rizzuto returned to Canada after serving an eight-year sentence for his role in the killing of three leaders of New York's Bonanno crime family