BACKGROUND: Infants and young children are obligate nose breathers; therefore, a transnasal route seems the logical delivery method of inhaled aerosols. The efficiency of aerosol delivery depends on several factors, such as interface, type of nebulizer, and patient age and breathing pattern. We hypothesized that the use of a vibrating mesh nebulizer, a tight-fitting face mask, and a head model and breathing pattern of an older child would result in a higher lung dose. We also hypothesized that the use of an anatomically correct model would more accurately reflect lung dose than models that do not include airways. METHODS: A model comprising a breathing simulator and an anatomically correct model of a 7-month-old infant and a 5-y-old child with an interposed collection filter (lung dose) were used. Breathing patterns of a newborn, infant, and child were used with 7 interfaces. A continuous output and a vibrating mesh nebulizer were loaded with albuterol sulfate solution (5 mg/3.5 mL) and operated for 5 min. Albuterol mass was determined via spectrophotometer (276 nm). RESULTS: Lung dose varied between 0 and 3%. The jet nebulizer was more efficient than the vibrating mesh nebulizer. The front-loaded mask was the most efficient interface. We also found that higher tidal volumes were associated with higher lung doses and that the use of a larger airway model resulted in a lower lung dose. Finally, the model showed a good correlation with in vivo data and rendered lung doses severalfold lower than previous data obtained with oral models. CONCLUSIONS: Careful pairing of the aerosol generator and interface is very important during transnasal aerosol delivery.