OBJECTIVES: This study was conducted to study the Computed Tomography (CT) characteristics of wall thickening in case of benign and malignant lesions of the colon and rectum, to evaluate the effectiveness of CT in differentiating benign and malignant colorectal lesions and to evaluate the role of CT in pre-operative tumor staging of colorectal malignancies. SOURCE OF DATA : Data was collected from 20 patients with wall thickening involving the colorectal region on CT, referred to the department of Radio Diagnosis. MATERIALS AND METHODS: A retrospective study was conducted over a period of 4 months from September 2013 to December 2013. In this study, 20 patients with wall thickening involving the colon and rectum on CT were included. CT findings were finally confirmed with histopathological diagnosis. RESULTS: Out of the 20 patients, 12 patients were males and 8 were females. Most of the affected patients were in the age group of 50-70 yrs. All the 18 malignant lesions were correctly diagnosed on CT.1 of the 2 benign lesions was correctly diagnosed on CT. The other one was an inflammatory lesion of the colon which was diagnosed as malignancy on CT. The CT features of benign lesions were homogenous attenuation, mild symmetric wall thickening and diffuse involvement of the bowel. The CT features of malignant lesions were heterogeneous attenuation, marked asymmetric wall thickening and focal involvement of the bowel. In the CT staging o f malignant lesions, 3 of the 4 cases were correctly staged as T1/T2 lesions. 10 of the 12 cases were correctly staged as T3 lesions and all the 2 cases were correctly staged as T4 lesions. CONCLUSIONS: CT proved to be an excellent modality in the diagnosis and differentiation of benign and malignant lesions of the colon and rectum. CT is also useful in the staging of malignant lesions which helps in proper planning of surgery and further management of the patient. Besides identifying the lesion, CT provides further information regarding pericolic abnormalities associated with the lesion, presence of lymph nodes, infiltration of adjacent viscera and the presence of distant metastases.