Maha M. A. Elmadah,¹Samah H. Elmeadawy²,  Wael M. S.Saadeldin³ ,  Ahmed A. Elsouda^{4 1}B.D.S Mansoura University-Egypt 2007 ² Associate Professor of Oral Medicine & Periodontology, Faculty of Dentistry, Mansoura University ³Assistant Professorof Diagnosis and Oral Radiology, Faculty of dentistry, Mansoura University ⁴ Assistant Professor of Endodontic Faculty of dentistry, Mansoura University Abstract: Background:. Root fracture (RF) is a complication that often leads to teeth extraction. A VRF is the most severe  type  of  longitudinal  defect .Vertical root fracture (VRF) is a longitudinal root fracture, extending from the root canal to the periodontium. Three-dimensional diagnostic imaging technique may be useful for the detection of VRF. Aim:This study aimed to: evaluate the accuracy of cone beam computed tomography in detection of vertical root fracture linear measurements and orientation in human extracted teeth.  Also, to evaluate the effect of endodontic obturation on the diagnosis of vertical root fracture. Additionally, to develop a task specific radiation protocol to diagnose vertical root fracture in both endodontically and non-endodontically treated teeth.. Materials and Methods:this study was conducted on 60 teeth. The teeth  were divided into two groups: group I included 30 endodontically treated and obturated teeth, group II  include 30 endodontically treated but not obtureted teeth. then all teeth of two groups were scanned with i-CAT  CBCT machine after fracture induction with different three voxel sizes o.1, o.2, o.25 mm. Additionally all teeth were inspected by stereomicroscope to confirm the presence of fracture.  Then the length of the fractures were measured to act as the gold standard to CBCT linear measurements. Result: The results of the present study, showed that CBCT 0.1 , 0.2 & 0.25 had the same validity measures in fracture diagnosis as compared to stereomicroscope with 100.0% sensitivity and negative predictive value, 96.4% accuracy, 96.3% positive predictive value with the least measure was specificity 50.0%. However, there was a high statistically significant strong positive correlation between  stereomicroscopeand different CBCT voxel size readings. conclusions: we  can conclude that CBCT has an superior value in detection of vertical root fracture in endodonticaly treated teeth compared to stereomicroscope. Recommendations : Further clinical  studies are recommended  to confirm the results about the role of CBCT as a new imaging modality in the detection  of the vertical root fracture.