Oxidative stress is one of the risk factors of colorectal carcinogenesis. In inflammatory reactions the activated leukocytes produce mutagenic and mitogenic free radicals, thereby promoting tumor formation. Obesity, hyperlipidemia and hyperinsulinemia increase the energy supply of epithelial cells, thus leading to deregulation of mitochondrial electron transport chain. The latter results in increased free radical production that causes impairment of cell cycle regulation, mutations, and unrestricted proliferation of damaged cells. Aim: Evaluation of some parameters of antioxidant and nutritional status in patients with benign or malignant colorectal neoplasms. Methods: assessment of nutrient intake, measurement of some anthropometric parameters (body height, body weight, waist, hip and arm circumference, waist/hip ratio), determination of serum prealbumin level, evaluation of the biomarkers of antioxidant status (superoxide dismutase and glutathione peroxidase activities, levels of uric acid and albumin, total antioxidant status, free radical scavenger capacity), determination of the concentration of advanced oxidation protein products (AOPP) and malonyldialdehyde. Results: In patients with malignant tumors the dietary fiber, folate and vitamin A intakes were below the optimal level, and the serum prealbumin concentration was lower than in patients with benign lesions. There was a high incidence of overweight and obesity among patients. Significant difference was found between diseased subjects and healthy controls in terms of the biomarkers of antioxidant status, such as free radical scavenger capacity, concentrations of advanced oxidation protein products and malonyldialdehyde and glutathione peroxidase activities. Conclusions: The insufficient folate and vitamin A intake, the high incidence of overweight and obesity, and the abnormal values of the biomarkers of antioxidant status observed in the study groups seem to support the correlation between colorectal tumor, nutritional and antioxidant status.