There is provided an automotive air conditioning system comprising a primary blower disposed at a front part of a vehicle having a passenger compartment constituted by a front-seat side space and a rear-seat side space, a case disposed in the front part of the vehicle in such a manner that air is caused to flow from one end to the other end thereof by means of the primary blower and having a lower opening which is opened therein at a lower portion at the other end thereof, a heat exchanger disposed within the case, a scroll case disposed below the case and having opened therein an outlet and an inlet connecting to the lower opening, an centrifugal fan accommodated in the scroll case and having a rotating shaft which is oriented in a substantially vertical direction, a secondary blower having driving means for driving the centrifugal fan, and a rear seat duct connected to the outlet and communicating with the rear-seat side space.