Intoduction: The most investigated precancerous states are: Barrett’s esophagus, atrophic gastritis and colonic adenoma. It is possible to visualize infiltration of lymphocytes (TIL – tumor infiltrating lymphocytes) into the tissue of malignant tumor. Lymphocytes with the expression of foxp3+ molecule (T regulatory lymphocytes) can be found among TIL. Their role in malignancies has been proven. However, it is not known if they are present in precancerous states. Conclusions:An increase in the number of Tregs in the lymphocytic infiltration of large intestinal polyps is observed at early stages of carcinogenesis. Proportions of various T-cell subpopulations in the infiltration vary considerably depending on the degree of dysplasia, especially in case of invasive colorectal cancer. Barrett’s metaplasia, either with dysplasia or without, is associated with an evident increase in the number of Foxp3 lymphocytes within the esophagogastric junctionmucosa. Restoration of lymphocyte balance in esophageal tissue may prevent malignant transformation of Barrett’s metaplasia. Significant increase of Foxp3+ lymphocyte count and significant change of Foxp3+/CD4+ ratio are present in invasive cancer stage.