The number of newly diagnosed cases of diabetes mellitus (DM) and various cancers is growing every year. Obviously, the presence of one disease significantly complicates the course of another. But it is still unclear whether diabetes potentiates the development of cancer or oncopathology will be the cause of carbohydrate metabolism disorders, and what effect the use of antidiabetic drugs has on the course of cancer.The purpose of this review was to establish a causal relationship between diabetes, hypoglycemic therapy and the development of oncopathology.Results. The hyperinsulinemia and hyperglycemia consistently increase the likelihood of tumor development not only in patients with diabetes but also in patients with prediabetes, and lead to some cancers, such as pancreatic, liver, stomach, colon, breast, kidney, lungs, etc. In addition, increasing or decreasing the risk of cancer may be a side effect of some antidiabetic drugs.Conclusions. Diabetes is a risk factor for cancer, especially hepatocellular, hepatobiliary, pancreatic, breast, ovarian, endometrial and gastrointestinal cancers. In general, treatment with sulfonylureas can increas the risk of cancer, while treatment associated with improved insulin resistance, such as metformin, may reduce this risk.It is obvious that many existing studies have ambiguous results and require correction due to organizational errors, ie it is necessary to conduct additional carefully planned and properly organized studies. In addition, given the importance of both diseases, we believe that diabetic patients need routine screening and orientation of medical personnel for early detection of oncopathology.