A substance delivery module (4) and apparatus (2) for delivering substance in aerosol form are disclosed. The substance delivery module (4) comprises a plurality of substance containers (90) and a plurality of pistons (76), with each substance container (90) being mounted in the module for cooperation with a dedicated piston (76). Another substance delivery module (4) is disclosed comprising a piston (76) defining a delivery axis (150) and a substance container (90), moveably mounted with respect to the piston (76). The substance container (90) is moveable along the delivery axis (150) and may for example be moved towards and onto the piston (76). Either of the substance delivery modules (4) may be assembled with an aerosol generator (10) and an aerosol delivery conduit (14) in fluid communication with the aerosol generator (10) to form an apparatus (2) for delivering substance in aerosol form. The apparatus (2) may further comprise a control module (6).