A device for flow rate limitation at low differential pressures, particularly for limiting the volumetric inhalation flow during inhalation of therapeutic aerosols, consists of a housing 11 including an aspiration orifice 14, an inhalation orifice 15 and a flow passage 23 disposed therebetween. The flow passage has a flat elongate cross-section with flexible large-area walls 18, 20 having a cross-sectional area adapted to be reduced, as a function of the differential pressure prevailing between the inhalation orifice and the aspiration orifice, as well as of the flexibility of the material of the walls, to a size appropriate for a predetermined volumetric maximum inhalation flow.