PURPOSE This retrospective study compared computed tomography (CT) imaging to routine dental periapical radiographs in diagnosing radiolucencies around endodontically treated teeth. MATERIALS AND METHODS Of the 244 CT scans evaluated, 104 had no teeth on the scan. On the remaining 140 scans, 353 teeth fell into the following categories: 59 maxillary molars, 30 mandibular molars, 66 maxillary premolars, 56 mandibular premolars, and 141 anterior teeth. Positive and negative predictive values were calculated, as were sensitivity, specificity, and prevalence assuming the CT scan was the test standard. RESULTS For the total tooth population periapical radiograph - CT slice sensitivity was 52, specificity was 90, the positive predictive value (PPV) was 97, the negative predictive value (NPV) was 25, and the prevalence 85. CONCLUSION In the population studied, the CT scan had a greater ability to show radiolucencies that were not evident on periapical radiographs.