Objectives: To assess the effectiveness of the „Narrow-band imaging international colorectal endoscopic classification“ in differentiating between deep submucosal invasive cancer and adenomas and to assess its effectiveness in differentiating between adenomas and hyperplastic polyps. Object is also to determine the frequency of polyps in individual parts of the large intestine and to determine the distribution of the pathohistological types of polyps in individual parts of large intestine. Study design: Prospective observational study. Patients and methods: Total of 122 patients were prospectively enrolled in this study, 77 males and 45 females. All of these patients were referred to colonoscopy due to various indications. Colonoscopies were performed using Olympus CF-H185L EVIS EXERA III and Olympus CF-H185I EVIS EXERA III colonoscopes. Patient's gender, age, number of polyps, size of each polyp and localization of each polyp were recorded. All of the detected polyps were viewed under NBI and after the endoscopic prediction of polyp histology using the NICE classification was made, polyps were resected and retrieved individually for pathological examination. The criterion standard for validation of real-time predictions was the pathologist's report of polyp histology. All statistical analysis were performed with SPSS statistics for Windows, version 23. The primary outcome measures for the predictive validity of the NICE classification for endoscopic assessment of the histology of colorectal polyps was the negative predictive value of an adenomatous prediction and the negative predictive value of deep submucosal invasive cancer. Results: NICE classification has proven to be relatively effective diagnostical method in differentiating between deep submucosal invasive cancer and adenomas (the sensitivity was 28.6%, specificity was 98.9%, positive predictive value was 66.7%, negative predictive value was 94.4% and accuracy was 93.6%), however it has not proven to be effective in differentiating between adenomas and hyperplastic polyps (the sensitivity was 82.5%, specificity was 87%, positive predictive value was 96.6%, negative predictive value was 52.6% and accuracy was 83.3%). There was statistically significant difference in size between hyperplastic polyp and adenoma (T= 7.64, p<0.001) and statistically significant difference in size between hyperplastic polyp and adenocarcinoma (T= 4.5, p=0.003). There was no statistically significant difference in size between adenoma and adenocarcinoma (T= 1.92, p=0.089). Total of 135 polyps were resected - 38 in rectum (28%), 63 in sigmoid colon (47%), 8 in descending colon (6%), 6 in transverse colon (4%), 9 in ascending colon (7%) and 11 in cecum (8%). According to the pathohistological diagnosis of the retrieved samples, the prevalence of hyperplastic polyps amongst patients was 17% (23 polyps). The prevalences of adenomas and adenocarcinomas were 77% (104 polyps) and 6% (8 polyps), respectively. There was no statistically significant difference between the pathohistological diagnosis of polyps and localization of polyps (p=0.245). Conclusion: This study has pointed out certain benefits of the NICE classification as a diagnostical method for real-time prediction of the colorectal polyp histology. Further clinical studies with greater number of patients included should be conducted to assess the generalizability of this classification. It is also necessary to avoid limitations noted in our study.