1. A method of assessing lung function using a first set of lung volumetric images obtained at inspiration and a second set of volumetric images obtained at expiration, the method comprising: a) processing the first and second set of images to identify known anatomical structures of the lungs; b) registering the first set of images to the second set of images to match voxels of the first set of images to voxels of the second set of images as matched pairs of inspiratory and expiratory voxels; c) calculating a probability of a lung characteristic at each of a plurality of locations, each of the plurality of locations corresponding to one of the matched pairs of voxels of step b); and d) displaying a result of step c) on a display, the displayed result comprising the calculated probability or a different value derived from the calculated probability at each of a plurality of locations of matched pairs of voxels.