There is provided an electrically operated aerosol-generating system (70) comprising an aerosol-generating device (50), a removable aerosol-forming cartridge (30) and a removable heater (10), wherein the removable aerosol-forming cartridge and the removable heater are provided separately from each other. The aerosol-forming cartridge (30) comprises at least one aerosol-forming substrate, and the heater (10) comprises at least one electric heater element (14) and first electrical contacts (16) connected to the at least one electric heater element (14). The aerosol-generating device (50) comprises a main body (51) defining a main cavity and at least one opening for receiving the aerosol-forming cartridge (30) and the heater (10) within the main cavity. The aerosol-generating device (50) also comprises an electric power supply and second electrical contacts connected to the electric power supply. When the aerosol-forming cartridge (30) and the heater (10) are both received within the main cavity, the first electrical contacts (16) are in contact with the second electrical contacts and the heater (10) is arranged to heat the aerosol-forming substrate. The aerosol-forming cartridge (30) and the heater (10) are substantially flat, and the main cavity, the aerosol-forming cartridge (30) and the heater (10) are arranged such that the aerosol-forming cartridge (30) and the heater (10) are substantially parallel and adjacent to each other when received together in the main cavity.
