Introduction. Tomography images provide sufficient detail for estimating the vertical and horizontal dimensions of alveolar bone and reducing surgical injuries. This study evaluated the role of spiral tomography in measuring mandibular alveolar bone width. Methods. Cross-sectional tomography slices were taken using a Cranex Tome unit at three or four different locations on each side of three chosen mandibles, such that all the locations were distal to the mental foramen. In addition, artificial soft tissues were reconstructed using Play-Doh modeling clay. On the tomography image, a line was drawn from the crest to the inferior border of the mandible (MC), and the bone height to the mandibular canal and bone width were measured at one-third, two-thirds, and one-half MC, and the mandibular canal levels. Then, the mandibles were sectioned at the same sites, and the bone sections were measured. For statistical analysis, the sign test analysis was used.Results. There was a statistically significant difference between the tomographic and real anatomical bone width at one-half and one-third MC, and the canal level (P < 0.05), while the difference between tomography and bone section measurements were not significant at two-thirds MC, or, the bone height to the mandibular canal (P > 0.05). Conclusions. The bone width on tomographic images was overestimated by between 2.3 and 0.1 mm. Therefore, caution should be exercised when evaluating bone width measured from tomography images. In most locations, the measured height to the canal was underestimated by between 0.1 and 2.7 mm, which confirmed the safety of spiral tomography for estimating the distance related to the mandibular canal.