Background and Aim: Colorectal cancer is the third most common cancer and the fourth most frequent cause of cancer deaths worldwide.  The aim of this study to compare the diagnostic performance of abdominal  ultrasound and multidetector CT in detection of colorectal cancer. Methods: this study included fifty patients were presented to surgical department of  Mit Ghamr oncology center. All patients were examined on MDCT to show presence of the cancer. then examined by abdominal ultrasound  to  evaluate ability of ultrasound to detect the cancer. Results: fifty patients were included (28 men and 22 women) had a mean age of 47.5years (range 28-70years). Our study results suggested  that abdominal ultrasound had sensitivity  and specificity in diagnosis of cancer colon were  82.4%  and 87.5 % respectively. The accuracy of US  was 84%. For  MDCT, sensitivity and specificity  of  cancer colon    were 100% and 93.8 respectively. The accuracy of MDCT was 98%. Conclusion: ultrasonography is a useful initial screening tool for colorectal cancer in patients presenting with abdominal distension. Compared with MDCT scanning and other modalities. Ultrasonography is easily available; does not involve radiation, bowel preparation, or sedation; carries no risk of colonic perforation; and is less expensive. Further studies to confirm the usefulness of ultrasonography for diagnosis of colorectal cancer are warranted. CT is valuable in preoperative assessment and staging of colorectal cancer as well as in postoperative surveillance for recurrence. Rapid advances in technology will likely continue to improve the accuracy and usefulness of CT.