BACKGROUND: Colorectal cancer is the second most frequent cancer and adenomas are widely accepted as precursors to colorectal cancer. Diagnosis and removal of adenomas are recommended to reduce cancer incidence and mortality. The current diagnostic methods include sigmoidoscopy and colonoscopy. Lately, CT- and MR colonography have emerged as non-invasive methods for colon imaging. METHODS: At present, CTC and MRC require bowel preparation. However, preliminary studies have been carried out without colon preparation. After the colon has been filled with air or contrast, the patient is scanned in the supine and prone positions. Data are then downloaded to a workstation for post processing and image-analysis. RESULTS: Results have shown a high sensitivity and specificity for polyps > or = 10 mm, comparable to the sensitivity of conventional colonoscopy and superior to double contrast barium enema. CONCLUSIONS: With the exponential development in computer processing power, CT- and MR colonography holds the promise for future colon examination with the advantages of non-invasiveness, no need for sedation, and probably no bowel preparation. A major disadvantage, however, is the radiation dose during CT colonography. Future developments with the use of "intelligent" computers, better resolution and faster examinations will make CT and/or MR colonography realistic options to replace conventional diagnostic colonoscopy.