Budesonide is a poorly water soluble corticosteroid used in the treatment of asthma and chronic obstructive pulmonary disease (COPD). The aim of the present study was to develop micronized porous particles containing budesonide in a mannitol-based dry powder formulation using spray freeze drying (SFD) technique. Hydroxy propyl beta cyclodextrine (HPbCD) and/or L-leucine were employed as complementary excipients and their effects on the particle shape and morphology of processed powders were evaluated. As well, the produced particles were characterized in terms of thermal behavior, porosity, dissolution rate and suitability for pulmonary delivery. The results demonstrated that aerosolisation performance of the microparticles containing both L-leucine and HPbCD were considerably improved in comparison to other formulations and the fine particle fraction (FPF) increased substantially. Different ratios of excipients resulted in the formation of particles with different aerodynamic behaviors. (C) 2014 Elsevier B.V. All rights reserved.