CBCT units provide axial, coronal and sagittal multi-planar reconstructed images without magnification. Also, panoramic images without distortion and magnification can be generated with curved planar reformation. CBCT displays 3D images that are necessary for the diagnosis of intra bony defects, furcation involvements and periapical defects. Materials   and Methods: Five dry mandibles were used in this study. Preapical defect related to molars are created were of varying shapes and sizes mimicking periapical pathosis mandible,,the perapical defects were scanned using 3 different CBCT machines Results: there was no statistical difference between  the volume calculated from the Acuuitomo CBCT and the volume calculated from the physical measurement, there was a  statistical difference between  the volume calculated from the Newtom  and Planmeca CBCT and the volume calculated from the physical measurement, Conclusions:CBCT  is a valuable imaging modality in estimating the volume of perapical defects