A CPAP system includes a flow generator (10), a patient interface (50), an air delivery conduit (20) that interconnects the flow generator and the patient interface, wherein the air delivery conduit has an internal diameter of less than 19 mm. Preferably the air delivery conduit has an internal diameter of between about 10 mm and about 18 mm. The CPAP system may also include a controller for compensating for pressure swings and/or increased impedance within the system. Preferably the blower includes a low inertia blower.