A method for treatment of patients with cystic fibrosis by providing an inhalable aerosol comprising a mucolytic compound (dornase alpha) administered into a patients lungs according to a specific treatment protocol setting comprising a mucolytic drug containing aerosol having particles with a predetermined mass medial aerodynamic diameter (MMAD) delivered predominantly to a peripheral lungs using a nebulizing system able to administer said aerosol with overpressure and under controlled breathing conditions.
