Purpose: The aim of this study was to compare the relative accuracy of the ridge-mapping method against that of standard computed tomography (CT). Materials and Methods: Consecutive partially edentulous subjects requiring dental implants were recruited for this prospective study. Vacuum-formed radiographic templates with reference points were used for the ridge-mapping procedure and CT scanning. Ridge-mapping measurements were translated onto study models, which were subjected to CT scanning with the templates in place. CT images of the study models obtained from the ridge-mapping method were compared with CT images of the subjects. The data were analyzed with the Wilcoxon signed-rank test. Differences were considered significant if P .05. Results: Fourteen subjects were recruited and a total of 21 implant sites were evaluated. The ridge dimensions measured by the bone-mapping method and CT scanning were significantly different (P .05). The mean difference ranged from 0.3 to 0.5 mm, and large variations were found in the sulcus region. Conclusion: Measurements of the alveolar bone dimension using the ridge-mapping method are different from CT scanning, with a mean difference of about 0.4 mm. Keywords: computed tomography, dental implant, measurement, ridge mapping