Swellable particles for delivery of a drug or other working agent to the pulmonary system are provided. The swellable particles include a dehydrated (dry) aerodynamic particle diameter of 5 µm or less to enable delivery to the respiratory tract, such as for example to the tracheo-bronchial airways of the upper respiratory tract and/or to the alveolic regions of the deep lung, and a hydrated particle diameter that is greater than 6 µm volume mean diameter to retard or prevent their phagocytosis by the macrophages present in airways of the respiratory tract.
