The invention relates to micronised particles of a low-dosage strength active ingredient to be used in dry powder formulations for inhalation and methods for preparing them. In particular the invention provides micronised particles of low-dosage strength active ingredients which can easily and homogenously disperse in a dry powder formulation to be administered by means of a dry powder inhaler device. The invention is also directed to the formulations thereof in the form of powders for inhalation.