Abstract: An air-conditioning device especially for ceiling placement with low build-in height and comprising at least one preferably vertically oriented heat exchanger, with substantially horizontal percolation of the room air and at least one ventilation channel for fresh air provided substantially parallel to and within a small distance from the heat exchanger, at its outlet side, a downwards open air chamber provided between the ventilation channel and the heat exchanger, and air nozzles provided in the channel side wall of the ventilation channel facing the air chamber, which are directed towards the outlet of the air chamber. The ventilation channel is provided with a preferably convex channel wall which diametrically extends substantially from the upper corner of the ventilation channel to the lower corner of the ventilation channel. The heat exchanger and the ventilation channel are arranged with a downwards, diverging open air space.