An air-conditioning system for the passenger compartment of a vehicle. The air-conditioning system includes an air-treatment unit and with a series of ventilation outlets distributed inside the passenger compartment and connected to the air-treatment unit. Some of the ventilation outlets are mounted on the side surface of a tubular body, which is set in a bottom portion of the passenger compartment. An internal pipe communicates with the air-treatment unit, and is mounted to oscillate about a longitudinal axis thereof.