Objective: The aim of this study was to compare the results of ultrasound and CT assessment in preoperative staging of colonic cancer, and to determine whether CT offers any benefits beyond ultrasound. Patients and methods: Sixty-one cases of intraperitoneal colon cancer were assessed by preoperative abdominal ultrasound and CT. The ultrasound and CT findings were assessed for ascites, hepatic and peritoneal metastases, invasion of adjacent organs, and findings of other diseases. Results: The sensitivity rates of CT for liver metastases, adjacent organ invasion, ascites and peritoneal metastases were 81 %, 25 %, 29 % and 20 % respectively, while those of ultrasound were 69 %, 6 %, 43 % and 0 %, respectively. Both methods had similar sensitivity, specificity and accuracy rates regarding the detection of all criteria. Ultrasound was more sensitive for detecting ascites and liver metastasis when compared to peritoneal metastasis and invasion (p<0.05). CT allowed the detection of liver metastasis to be more sensitive when compared to the other three criteria (p<0.05). In addition to ultrasound, CT gave no more additional knowledge indicating the necessity of altering the clinical management in patients. Conclussion: The first-line scanning technique should be the ultrasound and there is no need for CT scan, should no abnormalities be found upon ultrasound examination. CT investigation plays a role in cases where the ultrasound findings are suspicious.