A cartridge assembly having a proximal end and a distal end for use in an aerosol- generating system comprises: a cartridge (2) comprising: a first compartment (4) having a first air inlet (10) and a first air outlet(14)； and a second compartment (6) having a second air inlet (18) and a second air outlet (22)； and a mouthpiece (30) partially surrounding the cartridge (2), the mouthpiece (30) having a third air outlet. The cartridge (2) and the mouthpiece (30) are longitudinally movable relative to one another between a retracted position in which a proximal end of the mouthpiece (30) abuts a proximal end of the cartridge (2), and an extended position in which the proximal ends of the mouthpiece (30) and the cartridge (2) are longitudinally spaced apart so as to create a chamber (36) there between in fluid communication with the first (14), second (22) and third (32) air outlets. In the retracted position the first (10) and second (18) air inlets and the first (14) and second (22) air outlets are obstructed by the mouthpiece (30) and the third air outlet (32) is obstructed by the cartridge(2). In the extended position air may be drawn into the chamber (36) along a first airflow pathway extending from the first air inlet (10), through the first compartment(4), to the first air outlet (14) and a second airflow pathway extending from the second air inlet(18), through the second compartment(4), to the second air outlet (22), and out of the chamber (36) through the third air outlet (32). An aerosol- generating system comprises the cartridge assembly and an aerosol-generating device (38) comprising a cavity (40) for at least partially receiving the cartridge assembly and a heater (42) for heating one or both of the first (4) and second (6) compartments of the cartridge (2) of the cartridge assembly.Una unidad de cartucho con un extremo proximal y un extremo distal para su uso en un sistema generador de aerosol comprende: un cartucho (2) que comprende: un primer compartimie
