The aim of our study is to examine the possibility of individualizing aerosol therapy, by determining the ideal diameter of the inhaled particles and the optimal breathing pattern, using a computerized simulation program. In order to find the optimal breathing pattern, we used different variations of the tidal volume and breathing period. We tried to determine the ideal particle diameter by carrying out a series of simulations for particles with diameters ranging from 1 to 10 microns. Our results show that increasing the particle diameter will lead to higher deposition values in the upper respiratory regions and bronchi, and smaller values in the acinary regions of the lung. Repeated simulations have led to two different ideal particle diameters, according to the localization of the desired effect. This way, for the bronchial regions the ideal particle diameter is 10 microns, and for the acinary regions 2 microns.