Abstract. A method for quantitative assessment of tree structures is reported allowing evaluation of airway tree morphology and its associated function. Our skeletonization and branch–point identification method provides a basis for tree quantification or tree matching, tree–branch diameter measurement in any orientation, and labeling individual branch segments. All main components of our method were specifically developed to deal with imaging artifacts typically present in volumetric medical image data. The proposed method has been tested in a computer phantom subjected to changes of its orientation as well as in repeatedly CT-scanned rigid and rubber plastic phantoms. In this paper, validation is reported in six in vivo scans of the human chest.