Spray booth (21) for applying paint on basically flat parts (22), said spray booth having a plenum (24) and comprising a conveying system (25) for conveying the flat parts (22) to be painted, at least a device (23) for applying paint on said moving parts, and at least a suction system, wherein the plenum (24) of the spray booth has a semi-cylindrical shape, having its axis perpendicular to the direction of the advancing part (22).