The fire broke out at Murrayburn Place in Edinburgh at 1.12am.
Two men were inside and both suffered smoke inhalation.
One was also taken to Royal Infirmary of Edinburgh for minor burns to his hand and arm.
A Lothian and Borders Fire Service spokeswoman said: “It was a fire within the living room that was caused by a cigarette catching a sofa alight.
“Two male occupants suffered from smoke inhalation and one also had burns on his arm.
“The fire was extinguished prior to our arrival.
“One of the men was taken to the Edinburgh Royal Infirmary for further check-up and the other refused to go to hospital.
A Scottish Ambulance Service spokeswoman said: “We were called at 1.28 this morning to patients who suffered smoke inhalation and burns.
“One patient travelled to hospital with minor burns.”