Aims:The aim of the present study was to evaluate the accuracy of Cone Beam Computed Tomography (CBCT) measurements of alveolar bone defects caused due to periodontal disease, by comparing it with actual surgical measurements which is the gold standard.Materials and Methods:Hundred periodontal bone defects in fifteen patients suffering from periodontitis and scheduled for flap surgery were included in the study. On the day of surgery prior to anesthesia, CBCT of the quadrant to be operated was taken. After reflection of the flap, clinical measurements of periodontal defect were made using a reamer and digital vernier caliper. The measurements taken during surgery were then compared to the measurements done with CBCT and subjected to statistical analysis using the Pearson's correlation test.Results:Overall there was a very high correlation of 0.988 between the surgical and CBCT measurements. In case of type of defects the correlation was higher in horizontal defects as compared to vertical defects.Conclusions:CBCT is highly accurate in measurement of periodontal defects and proves to be a very useful tool in periodontal diagnosis and treatment assessment.