Colon preparation technique is a major determinant factor for patient compliance and polyp detection in computed tomographic colonography (CTC). The purpose of this study is to compare three different colon cleansing techniques in terms of patient discomfort, sensitivity and specificity. The following colon cleansing methods were compared in 20 patients each: 1. standard colonoscopy cleansing (ScCl) the day of the examination, based on polyethylene glycol (PEG), 2. a slightly reduced cleansing (RcCI) the day prior to the examination, based on a combination of diet, bisacodyl and a reduced intake of PEG, and 3. a cleansing with dietary fecal tagging (FT) the day prior to the examination, based on a combination of diet, bisacodyl, magnesium citrate and a dedicated barium suspension. ScCl resulted in a clean colon, but produces fluid levels hampering a complete CTC and possibly resulting in false negative diagnosis. RcCl reduced the problem of fluid levels, but was faced with the problem of fecal residues, resulting in false positive diagnosis. FT offered the possibility to obtain a dry colon, with labelled fecal residues, thus reducing false positive findings. Optimisation of the diet and replacement of PEG by magnesium citrate in FT reduced the preparation related discomfort and improved the final opinion. FT is the preferred colon cleansing technique because, compared to ScCl, fluid levels are reduced, and compared to RcCl, differentiation between faecal residues and polyps is improved. Moreover, FT reduces preparation related discomfort, compared to both RcCl and ScCl.