The Narrow Banding Image NBI-Colonoscopy and Optical Magnification is a useful method for evaluation in vivo of capillary pattern and pit pattern of colorectal polyps. To evaluate the usefulness of NBI and Optical Magnification in differential diagnosis of colorectal polyps using Sano-Emura and Kudo's Classifications. Between january and may 2010, 86 colonoscopies were analyzed by two colonoscopists; 136 polyps were found and histologically analyzed. All polyps under 10 mm (119) were evaluated in accord with Sano-Emura and Kudo's classifications; data was analyzed together with an epidemiologist in cancer. The sensitivity, specificity and diagnostic accuracy was 97.3%, 90.7% and 94.9%, respectively, for Sano-Emura's c lassification. The sensitivity, specificity and diagnostic accuracy was 94.7%, 90.6% and 93.2%, respectively, for Kudo's Classification. The colonoscopy with NBI and Optical Magnification is an effective, reliable and simple method for Colorectal neoplastic and non - neoplastic differential diagnosis when Sano-Emura's and Kudo's Classifications are used.