An air diffuser for spreading and feeding out an exact amount of conditioned air, comprising an inlet 3 and a stationary hood part 6 connected thereto cooperating with an adjustable hood part 7 for variation of a spreading or feeding gap for the conditioned air. A spring 14 is provided between both hood parts, which are kept at a selected spacing by means of an adjusting screw. Said screw extends through the adjustable hood part via an opening with large allowance, so that the adjustable hood part can be tilted such, that a certain enlargement of the spreading gap on the one side is corresponded proportionally by a corresponding diminution on the diagonally-opposite side. Adjusting the screw changes the total flow through the gap. Tilting the hood part changes the distribution of the air without changing the total flow.