Functional imaging of the respiratory system is a new domain where the respiratory dynamics (such as airflow in the lungs and particle deposition) are studied by means of modern engineering techniques. A three dimensional model of a patient specific bronchial tree is constructed from a computed tomography scan. By segmenting the desired region of air from the set of images in the scan a well defined, smooth geometry of the airway can be extracted, meshed and exported to be used in a computational fluid dynamics (CFD) analysis. Together with the patient specific lung geometry the CFD analysis uses patient specific boundary conditions, extracted from clinical tests, to initialize the airflow in the respiratory system. Two experiments are simulated in this work by means of CFD computations. Careful treatment of the CFD boundary conditions made sure that the experimental circumstances are mimicked as reliable as possible. This leads to a good correlation with the experimental outcome. Not only trends like lung deposition in function of the size of particles but also absolute quantities are predicted well with the CFD computations. The positive outcome of the study is promising for pharmaceutical companies when regarding the development of new respiratory drugs. CFD can give an insight into regional particle deposition and how changes in particle characteristics can influence deposition.