OBJECTIVE: To compare lung deposition from a nebulizer and a pressurized metered-dose inhaler (pMDI)/holding chamber to determine their efficiency in aerosol delivery to children. Study design: Children with stable asthma (n = 17) aged 2 to 9 years inhaled in random order radiolabeled salbutamol from a nebulizer and a pMDI through a nonstatic holding chamber. Body and lung deposition of radiolabeled salbutamol was assessed with a gamma camera. RESULTS: Mean (absolute dose) total lung deposition expressed as a percentage of the nebulized dose was 5.4% (108 microg) in younger children (<4 years) and 11.1% (222 microg) in older children (>4 years). Mean (absolute dose) total lung deposition expressed as a percentage of the metered dose was 5.4% (21.6 microg) in younger and 9.6% (38.4 microg) in older children. CONCLUSIONS: For the same age groups we have shown equivalent percentages of total lung deposition of radiolabeled salbutamol aerosolized by either a nebulizer or a pMDI/holding chamber. However, the delivery rate per minute and the total dose of salbutamol deposited were significantly higher for the nebulizer.