A combustor for a gas turbine engine comprises a single skin liner defining a combustion chamber. The single skin liner has an inner surface facing the combustion chamber and an outer surface exposed to a coolant flow discharged in a plenum extending from the outer surface of the single skin liner to the engine casing. Cooling holes extend through the single skin liner. Cooling protuberances, such as fins or pin fins, project integrally from the outer surface of the single skin liner into the plenum, the cooling fins being interspersed between the cooling holes.