The invention relates to a method of ventilating a treatment cubicle such as a painting or spraying cubicle used for painting items such as vehicle bodies. The fresh air to be supplied to the cubicle is supplied via an air-permeable ceiling (1); an air supply chamber (2) is provided above the ceiling (1) and communicates with an inlet air chamber (3) which is connected via at least one aperture (4) to a fresh air supply system. The volume of fresh air flowing into the air supply chamber (2) can be regulated by altering the aperture (4). The proposed process is characterized by the fact that at least some of the fresh air drawn into the inlet air chamber (3) is forced to flow in a path parallel to the ceiling (1) for a predetermined distance before passing via the aperture (4) into the air supply chamber (2), while the parameters needed to regulate the fresh air flow are measured in the end region of the directed air stream. The invention also concerns a treatment cubicle. (Fig. 1)