Twenty people were also treated by paramedics at the scene in Charles Street, Glasgow, but did not need hospital treatment.
Four fire engines went to the scene when the alarm was raised at 5.16pm this evening.
They found a developing fire in the upper levels of a high rise flat.
The Scottish Ambulance Service said one adult was taken to Glasgow Royal Infirmary while two were taken to Queen Elizabeth University Hospital.
Two children were taken to the Royal Hospital for Children Glasgow.
All five were suffering from smoke inhalation.
A Scottish Fire and Rescue Service spokesman said: “Firefighters wearing breathing apparatus sets are currently tackling the blaze using a number of main firefighting water jets.
“Nearby residents to the scene are also being supported by a combination of firefighters and colleagues from the Scottish Ambulance Service and Police Scotland.”