TO THE EDITOR: We read with interest the article by East et al. (1) on the colonic surface visualization by computerized tomography (CT) colonography-simulated colonoscopy. With CT colonography simulation, they examined how much colonic surface is visualized by a standard optical colonoscope (field of view 140◦) and a wide-angle (170◦) colonoscope with or without a retrograde viewing auxiliary imaging device (RVAID;135◦). The percentage of colonic surface visualized by a simulated 140◦ and 170◦ colonoscope was 86.6% and 92.2%, respectively, and that in addition with an RVAID was 98.7% and 98.9%, respectively. Although a simulated 140◦ colonoscope with an RVAID looks promising, with almost complete colonic surface visualization, we believe that the simulated method cannot be applicable to routine clinical settings because a retrograde viewing in the entire colon is infeasible. Due to the rapid progress of colonoscopic technology, optical colonoscopy is becoming increasingly popular for the management of colorectal diseases and is being considered the gold standard for the diagnosis of mucosal lesions (2). While the value of colonoscopy depends largely on the ability of endoscopists, incomplete colonoscopy by inexperienced hands and the risk of complications have been considered (2). Although colonoscopic polypectomy has been shown to reduce the incidence of subsequent colorectal cancers, some polyps, and even cancers, may be missed during colonoscopy because they lie outside the field of view, either hidden behind the semilunar folds, at the flexures, or in the lower rectum (3). Previous studies, including our study (2, 4–6), showed that an auxiliary device, a transparent hood, attached to the tip of a standard optical colonoscope was effective for total colonoscopy. Moreover, the technique requires less experience of endoscopists (2, 6). By depressing the semilunar folds, colonoscopy with the hood ensures good visual fields and easy recognition of the luminal continuity through the transparent wall of the hood at bends (2). On randomized controlled trials of colonoscopy with or without the hood (2, 6), more polyps are detected during colonoscopy with the hood. Although East et al. (1) did not address the issue of polyp detection in their study, focusing instead on colonic surface visualization as a surrogate, we believe that colonoscopy with the hood is a more practical and effective candidate. Because colonoscopy with the hood is simple, inexpensive, and readily available in most institutions, the technique should be performed in routine clinical practices for much colonic surface visualization, especially for more polyp detection.