A method for the prepn. of respirable zafirlukast monohydrate particles comprises the steps of prepn. of an aq. suspension of amorphous zafirlukast; size-redn. with conversion of the suspended zafirlukast into cryst. monohydrate nanoparticles; and isolation of the cryst. zafirlukast in the form of a dry powder.  Also provided are zafirlukast respirable particles characterized by comprising cryst. monohydrate zafirlukast.  Pharmaceutical compns. comprising the particles are also disclosed, as is the use of the particles or compns. for the treatment of respiratory diseases.