In the paper the foundations are presented of current inhalation therapy, particularly of that applied in childhood. The problems are discussed, concerning deposition of aerosols in the tracheobronchial tree achieved by various methods of aerosol generation. Various factors affecting the bioavailability of the inhaled drugs are defined. Particular attention is paid to the problems of safety of inhaled corticosteroid therapy, stability of the inhaled drugs and their influence on the pulmonary surfactant.