Combination drug microparticles of beclomethasone and salbutamol sulphate were encapsulated and coated with amino acids L-leucine, L-valine and L-phenylalanine in the gas-phase in an aerosol reactor. The aim was to combine opposingly soluble drug materials into single particles and also to explore the influence of amino acid surface composition and texture on particle morphology and fine powder aerosolization. The amino acid coating was employed by partial vapor deposition on drug particle surfaces. Carrier-free powder aerosolization was studied using two different types of inhalers, Twister ™ and Easyhaler® at two pressure drops, 2 kPa and 4 kPa, over the inhalers. The powder emissions from the inhalers were relatively good but the fine particle fraction (FPF) depended very much on particle integrity and sintering degree. The best results were obtained with the leucine coated samples when the particles were well separated whereas the worst results, particularly the FPF, was obtained with the phenylalanine coated samples due to a strong particle sintering i.e. fusing between particles. Moreover, the leucine rough coating performed the best aerosolization properties in terms of emission and fine particle deposition and also independency of applied pressure drop inhalation flow rate.