**3. Conclusions**

As we have explained, colonoscopy plays an important role in preventing colorectal carcinoma. In average risk populations for developing of cancer, it is one of the recommended screening strategies. In this population it has not yet been demonstrated which one is the most cost-effective strategy. What is unquestionable is the role of colonoscopy because of its therapeutic approach on the removal of lesions detected by other techniques or by its own. In high-risk populations, the only acceptable strategy is screening colonoscopy. The frequency of examinations is determined in each case by the particular risk of developing CRC. In some cases, such as patients with long-standing ulcerative colitis or individuals from families with Lynch syndrome, conventional colonoscopy is not enough, requiring using special techniques for endoscopic diagnosis, such as chromoendoscopy and magnification endoscopy.
