Abstract: A heating or air-conditioning system for a vehicle occupant compartment has an air distributor with a warm-air outlet which is connected with an air duct leading to a center plane the vehicle occupant compartment. A cold-air bypass controlled by a cold-air flap is provided for lowering the temperature of the warm air flowing out of the warm air outlet to the air duct. In the cold-air bypass, which has a relatively small cross-section, a throttling element is coupled with the cold-air flap such that the cold-air flap partially, to a defined extent, covers the warm-air outlet in the open position of the cold-air flap, thus maximally opening up the cold-air bypass. In addition, in this arrangement the throttling element completely opens up the warm-air outlet in the closed position of the cold-air flap, thus completely blocking the cold-air bypass.