Bowel preparation and colon distention represent two critical steps of CT colonography (CTC) examination. The ideal colonic preparation is still under debate. It is general consensus that patients should undergo a low-residue diet before the examination, and to ingest a cathartic agent the day before. Different cathartic agents are available. In order to improve sensitivity and specificity, "tagging" of residual fluids, in combination with the administration of a cathartic agent, is now routinely used. It consists in the administration, prior to CTC, of water-soluble iodinated contrast medium or alternatively diluted barium sulfate suspension. Since bowel cleansing is consistently the most unpleasant part of colonic examination, minimally-invasive preparation schemes (using mild or no laxatives at all), more comfortable and less demanding for patients, are now available. For reduced bowel preparations the combination with faecal/fluid tagging is mandatory. Gaseous colonic distention is another critical step since collapsed bowel is a frequent cause of missed lesions at CTC. The use of a rectal balloon catheter has been replaced by a thin rubber tube in order to improve patient compliance and to minimise risks of perforation. To further improve Patient comfort, automatic CO2 insufflation represents a possible alternative to room air. The administration of a spasmolytic agent is particularly useful in the case of colonic spasm, typically in sigmoid colon, and in patients with severe diverticular disease. The use of a MDCT scanner is mandatory and dedicated scanning protocols need to take into account radiation exposure, especially in individuals undergoing screening CTC. Learning Objectives: 1. To become familiar with the options available for bowel preparation, including the use of tagging agents, and to learn three examples of a bowel preparation regimen that 'works'. 2. To learn a step-by-step evidence-based approach to distending the colon (including spasmolytic agents, patient positioning, insufflation technique). 3. To appreciate optimum CTC acquisition parameters. 4. To become familiar with described complications (notably perforation) and how the risk may be minimised.