This study was performed to evaluate the usefulness of computed tomography (CT) in analyzing the three-dimensional structure of alveolar bony defects. The result showed that differences between CT film and actual readings from the cusp ridge to the bone crest were negligible, and the reading on CT film was underestimated approximately 1 mm at the distance from the cusp ridge to the bottom of the bony defect. By reading a series of CT films, one can easily evaluate the type of bony defects. Therefore, application of CT maybe useful for analyzing three-dimensional structure and diagnosis of the alveolar bony defects.