The present invention concerns a method for determining a respiratory condition or for assessing the efficacy of a treatment for a respiratory condition or for optimizing a treatment protocol for a respiratory condition in a subject comprising the steps of: a) obtaining image data concerning two or more three-dimensional images of the subject's respiratory system, which images have been previously acquired during an assessment period； b) calculating a specific three-dimensional structural model of the subject's respiratory system for each of the two or more three-dimensional images of step a)； c) comparing the three-dimensional structural models of step b) with each other to determine a respiratory condition or to assess the efficacy of a treatment for a respiratory condition or to optimize a treatment protocol for a respiratory condition.
