Montreal Police are asking for the public's help in finding 69-year-old John Charles Kwasniewski.
Kwasniewski left his Beaconsfield home for a walk on Wednesday and hasn't been seen since.
Family members are concerned because he left home without his medication and without warm outdoor clothing.
Kwasniewski stands at five feet and 11 inches and weighs 286 pounds.
Authorities say he may be confused and near the Lionel-Groulx metro station.
He was last seen wearing a brown bomber jacket, with wool trim and blue jeans.
Anyone with information is asked to call 9-1-1.