Virtual Colonoscopy is a new diagnostic tool , It can be used reliably with high sensitivity and less side effects and complications compared to Conventional Colonoscopy in detecting lesions in patients with medium-sized and large polyps , patients with colonic masses , patients with colonic strictures in that Conventional colonoscopy failed to pass the lesion & Virtual colonoscopy succeeded to complete the study.Virtual colonoscopy has the potential to uncover unexpected findings outside of the colon, potentially leading to serendipitous discovery of important diseases or unnecessary evaluation of incidental findings. The net effect is unclear. Virtual colonoscopy exposes patients to radiation. Repeated examination might lead to substantial cumulative radiation exposure with associated risk of excess cancer mortality.