Background: Colon cancer is one of the most common cancers in the world, and today screening with colonoscopy plays a significant role in early detection and prevention of the progression of this cancer. Materials and methods: This retrospective and cross-sectional study was done on 160 patients referred to gastroenterology clinics who have indications for colonoscopy according to criteria. Based on the presence or absence of adenoma in the colonoscopy, the patients were divided into two groups. The serum level of gamma glutamyl transferase was checked in the adenoma and non-adenoma groups, and the results were compared. Gamma glutamyl level above 32 U/l in women and 49 U/l in men was considered as the cut-off level. The results were analyzed with SPSS software. Results: No significant correlation was observed between age and Gamma GT level (R=0.031) and there was no significant relationship between gender and Gamma GT level (p: 0.58). But on the other hand, a significant relationship was found between having an adenoma and high gamma GT levels (p: 0.002). Conclusion: According to results, it can be concluded that age and gender factors do not relate to the high level of gamma GT, but the relationship between this enzyme and adenoma was significant. Therefore, it can be said that the high level of gamma GT is an influential factor in having adenoma.