Efficient aerosol therapy in young children is a challenge. The aerosol administration method requires special features, because young children can not perform an inhalation manoeuvre, breath usually through the nose and may be distressed during the administration. The prescribing clinician should be aware of the advantages and disadvantages of the different inhalation devices available, in order to select the proper device for each individual patient. For maintenance asthma therapy in young children the pressurized metered dose inhaler (pMDI) combined with spacer is the first choice for delivering aerosols. A facemask can be attached if a child is unable to breath through the mouth. A small leak of the facemask can reduce the dose delivered dramatically, therefore a good seal is crucial. Lung deposition can be improved by using a pMDI with extra-fine particles. However, even if the most optimal device is chosen, cooperation during administration remains the most important determinant for efficient drug delivery. During crying the dose to the lungs is minimal. Optimal aerosol delivery to the lungs of young children can be achieved with a good facemask seal, good cooperation of the child, with quiet breathing and an aerosol with small particles.