We present a system for computer aided diagnosis of bone tumors in the facial skeleton. There are many di erent lesions with radiographic manifestation in the jaws. Our system helps performing the di erential diagnosis of these. The input is a digitized orthopantomograph OPG in which the user marks the position of the lesion with a single mouse click. An active contour model then automatically nds the boundaries of the lesion. Gray-level histograms, MRSAR texture features and Gabor lter features are computed for the lesion region. These features are then combined and used to query a database containing expert-diagnosed reference cases. The result is a number of similar cases, with tumor position marked and with available expert annotations. We show good agreement between our results and di erential diagnosis given by humans. The system is also a suitable tool for training and education.