Objective： To compare the assessments of the presence or absence and the changes of post-treatment periapical lesions using periapical radiographs versus cone-beam computed tomography (CBCT). Methods: Imaging records were selected from a sample of 233 radiographic examinations (including periapical radiographs and CBCT) of patients with chronic apical periododontitis who received treatment and review in Department of Cariology and Endodontology of Peking University School of Stomatology. After testing the inter-observer and intra-observer agreement, two observers determined the pre-sence or absence of a periapical lesion and classified the changes of lesions in 4 categories: absence, reduction or enlargement of lesion, or uncertain. The differences between CBCT and periapical radiographs in detecting the presence or absence and the changes of periapical lesions were compared using McNemar test and Fisher’s exact test respectively. Results: In the study, 233 teeth were assessed with both periapical radiographs and CBCT images. Periapical lesions were detected in 178 teeth on CBCT scans and in 146 teeth on periapical radiographs. CBCT images revealed a significantly larger number of lesions than were revealed by periapical radiographs (P<0.01). There was disagreement on the changes of lesions between the two radiological technologies in 25% teeth, and the difference was statistically significant (P<0.01). Conclusion: Significant differences were observed between periapical radiographs and CBCT in detection of post-treatment periapical lesions and assessment of the changes of periapical lesions.