Objectives CT is nowadays an examination routinely performed in Crohn's disease (CD) patients. However, there are several ways to assess gastro-intestinal tract, in particular colonic segments. Aim of this study is to compare enterography-CT (E-CT), performed after oral administration of polyethylene-glycol solution (PEG-CT) versus enterography-CT performed also with water enema via rectum (ECT-WE) in patients with CD. Methods We have studied 79 patients with CD undergone to enterography-CT (42 evaluated with PEG-CT and 37 with ECT-WE) who have performed a lower endoscopy within 15 days before CT. CT results concerning large bowel were compared with endoscopic findings. Intestinal distension, discomfort of the patients, sensitivity, specificity and diagnostic accuracy were evaluated. Pearson test was used for statistical analysis. Results Degree of abdominal pain was significantly higher in patients underwent to ECT-WE compared to PEG-CT. Distension of the colon was significantly greater in patients studied with ECT-WE compared to those studied with PEG-CT. Values of sensitivity, specificity and diagnostic accuracy of PEG-CT and ECT-WE were respectively 77, 86.5 and 81%, and 89, 100 and 92% in comparison with endoscopy. Conclusions In patients with CD, ECT-WE allows the evaluation of large bowel in addition to small bowel better than PEG-CT.