Previous studies compared delivered dose results from a range of nebulizers; one finding was that the AeroEclipse II breath-activated nebulizer (Monaghan Medical Corp., Plattsburgh, NY, USA) produced a higher dose than other jet nebulizers. 1,2,3 These studies were performed with simulated adult breathing patterns and the AeroEclipse II nebulizer was used in breath-activated mode. For pediatric and low-flow patient breathing patterns it is required that the nebulizer is switched to continuous mode, as the inhalation flow is insufficient to trigger the breath activation of aerosol generation. In this study we investigated the output of the AeroEclipse II nebulizer in continuous mode, and compared it to a reference breath-enhanced nebulizer, the SideStream Plus nebulizer (Respironics Respiratory Drug Delivery (UK) Ltd, Chichester, UK). The nebulizers were tested with a pediatric facemask (small, disposable AeroEclipse II mask, Monaghan Medical Corp.) and attached to an ASL 5000 breathing simulator (IngMar Medical Ltd, Pittsburgh, PA, USA), which was programmed to reproduce a simulated pediatric breathing pattern (tidal volume = 151 mL, breaths per minute = 25, inhalation:exhalation ratio = 1:1). It was found that, in breath-activated mode, the inhalation flow was, as expected, unable to produce aerosol when a small, disposable AeroEclipse II facemask was used. When used in continuous mode, the AeroEclipse II nebulizer produced a lower emitted dose of salbutamol sulphate (5 mg/2.5 mL, Salamol Steri-Neb, IVAX Pharmaceuticals, West Yorkshire, UK), compared to the breath-enhanced SideStream Plus nebulizer.