A device for guiding air for an air conditioning system of a motor vehicle. The air conditioning system includes air outlets. The device is designed so that it encloses a volume and within the volume at least one air channel extending continuously from an inlet to an outlet is formed. The device is arranged in such a way that can be shifted in a continuously variable manner in a direction between two end positions, wherein the device in the end positions in each case closes an air outlet.The device may be arranged in an air conditioning system for a motor vehicle with means for conveying, for cooling and for heating an air mass flow, including a housing with a mixing chamber, in which the device for guiding air is arranged.