Aerosol-mediated drug delivery to the premature and term infant lung is consistently reported as achieving low levels of drug deposition. The variety of infant specific interventions and associated equipment available to the clinician mean that there is no consensus standard of care when it comes to aerosol therapy. The result is substantial variability in how aerosols are administered, and consequently, varying levels in the quality and success of therapy. The airway anatomy and respiratory physiology characteristic of these patients is manifested as low tidal volumes, rapid breathing rates, small bore airways and grossly, ‘stiff’ lungs. All these factors combine to reduce the opportunity for aerosol deposition.  The opportunity for deposition in the lung is furthered reduced by means of the filtering effect of low bore tubing and interfaces and protective ventilatory strategies, e.g. bias flow and I:E ratios favouring greater exhalation times. However, despite these low levels of deposition, therapeutic levels of administration may still be achieved. A worked example for a 2 kg neonate is provided that details how, despite a 0.5 % lung dose, delivery on a mg/kg basis can exceed that of a 69 kg adult receiving a 10 % lung dose for the same course of treatment.