The aim of this work was to evaluate the in vitro performance of a nebulized nanoemulsion formulation which had been optimised previously. To do so, a transparent nanoemulsion preparation containing 1.5 mg/ml of budesonide was prepared and diluted to achieve concentrations of 250 and 500 μg/ml budesonide. The in vitro characteristics of the diluted nanoemulsions were then compared with the commercially available suspension of budesonide (Pulmicort Respules®) when nebulized using a jet and a vibrating mesh nebulizer. A smaller MMAD with improved aerosol output was observed in the nanoemulsion preparations compared with the corresponding suspension formulations indicating an improved in vitro performance for the nanoemulsion-based preparations