Several applications of xenon-129 MR imaging are under development, including diffusion-weighted and relaxation-weighted imaging. These techniques take advantage of the fact that the rate of loss of xenon-129 polarization is significantly influenced by the local blood flow and concentration of molecular oxygen, as well as the restriction of xenon-129 diffusion by small airway space dimensions. These data can be used to create maps of the lung reflecting regional ventilation/perfusion and micro-airway sizes. Other data that can be obtained with xenon-129 MRI include the volumes of ventilated and unventilated lungs which can subsequently be analyzed to determine the homogeneity of gas distribution within the airspaces. These data can be used to study the structural and functional changes taking place in the lungs associated with pulmonary diseases like CF and asthma. It might provide a diagnostic tool that is able to detect pulmonary diseases more sensitively than the current gold standard measurements of spirometry and plethysmography, and thus prevent irreparable and irreversible damage to the lungs in the early stages of disease.