PURPOSE: We compared the use of diluted gastrografin enema- and air enema CT for the evaluation of the diagnostic accuracy of preoperative lesion detection and the staging of colorectal carcinoma. MATERIALS AND METHODS: Forty-two patients (43 lesions) with colorectal carcinoma, diagnosed by barium enema and/or colonoscopy, underwent preoperative diluted (2.5%) gastrografin enema CT, and in another 26 patients (27 lesions) with colorectal carcinoma, air enema CT was performed. The presence or absence of lesion, its spread (T), and peritumoral lymph node (N) were analyzed. All patients underwent surgery and pathologic confirmation was obtained. RESULTS: Gastrografin enema CT and air enema CT demonstrated the primary tumor in 97.7% (42 of 43) and 96.3% of cases (26 of 27), respectively. A comparison of gastrografin enema CT and the pathologic results showed that the disease was correctly staged as T2 in five of six cases, as T3 in 28 of 31, and as T4 in two of five. Using air enema CT, the disease was correctly staged as T2 in three of three cases, as T3 in 17 of 21, and as T4 in one of two. Overall, carcinoma was correctly staged by gastrografin enema CT in 83% of cases (35 of 42) and by air enema CT in 81% (21 of 26). Nodal involvement was accurately detected in 64% of cases (27 of 42) using gastrografin enema CT and in 69% (18 of 26) using air enema CT. CONCLUSIONS: These findings suggest that the use of gastrografin enema or air enema CT does not significantly affect the diagnostic outcome.