A patient warming blanket comprising at least two layers capable of forming a hollow air space between the two layers for receiving warm air from a heating unit via an inlet port at or near an end of the blanket. The two layers being arranged so that the hollow air space forms at least one tubular portion disposed longitudinally there within, and one of the two layers has at least a portion of its surface formed of porous material so that warmed air is delivered to said patient by diffusion through said porous material. The tubular portion has non- parallel sides such that the sides of the tubular portion are further apart from each other at a first end of the tubular portion closer to the inlet port than at a second end of the tubular portion remote from the inlet port.
