It is well known that a standard x-ray CT scanner provides reliable CT values denoting x-ray absorption of materials in the object. In recent years, a new CT scanner named "Conebeam CT" has been developed for maxillofacial medical treatment. However, there is a problem that the new scanner provides unreliable CT values. This report examines a quantitative verification of the conebeam x-ray CT images for dentomaxillofacial region using several calibration materials and attempts to correct the images.