The invention is directed to a process for the preparation of suspensions of drug particles for inhalation delivery, said process providing particles of optimised particle size and distribution homogeneously dispersed in the carrier. The process, which is also suitable for the preparation of sterile suspensions, includes the step of homogenising and micronising the formulation in a turboemulsifier provided with a high-potency turbine, optionally followed by a treatment in a high-pressure homogeniser. A further aspect of the invention is directed to a process for preparing micronised sterile beclomethasone dipropionate by gamma-irradiation.