Malignant cells exhibit increased levels of intracellular reactive oxygen species (ROS) and altered levels of antioxidant molecules. The aim of this study was to evaluate the serum levels of some antioxidants, pro- ducts of lipid peroxidation and protein oxidation, growth factor and cytokine in the serum of breast and non- small cell lung cancer patients. This study includes 20 patients with breast cancer, 20 patients with non-small cell lung cancer and 20 healty subjects with no cancer as controls. Superoxide dismutase (SOD), glutathione (GSH), nitric oxide (NO), malonyldialdehyde (MDA), advanced oxidation protein product (AOPP), tumor necrosis factor-alpha (TNF-a) and epidermal growth factor (EGF) were measured in the serums. Increased levels of lipid peroxidation, protein oxidation and epidermal growth factor; low levels of NO and TNF-a were observed in cancer patients. Elevated GSH concentrations and decreased SOD activities were found in the serum of all the cancer groups. The results of our study suggest that enhanced oxidative damage altered the levels of these molecules in cancer patients.