AIM: To evaluate the value of postprocessing techniques of CT colonography, including multiplanar reformation (MPR),virtual colonoscopy (VC), shaded surface display (SSD) and Raysum, in detection of colorectal carcinomas.METHODS: Sixty-four patients with colorectal carcinoma underwent volume scanning with spiral CT. MPR, VC, SSD and Raysum images were obtained by using four kinds of postprocessing techniques in workstation. The results were comparatively analyzed according to circumferential extent,lesion length and pathology patt of colorectal carcinomas.All diagnoses were proved pathologically and surgically.RESULTS: The accuracy of circumferential extent of colorectal carcinoma determined by MPR, VC, SSD and Raysum was 100.0%, 82.8%, 79.7% and 79.7%,respectively. There was a significant statistical difference between MPR and VC. The consistent rate of lesion length was 89.1%, 76.6%, 95.3% and 100.0%, respectively.There was a statistical difference between VC and SSD.The accuracy of discriminating pathology patt was 81.3%,92.2%, 71.9% and 71.9%, respectively. There was a statistical difference between VC and SSD. MPR could determine accurately the circumference of colorectal carcinoma, Raysum could determine the length of lesion more precisely than SSD, VC was helpful in discriminating pathology patts.CONCLUSION: MPR, VC, SSD and Raysum have advantage and disadvantage in detection of colorectal carcinoma, use of these methods in combination can disclose the lesion more accurately.