Salt stress affects general metabolic processes and enzymatic activities, leading to increased production of reactive oxygen species. During exposure to stress, antioxidant defense systems, in turn, begin to protect the cell from oxidative damage. The effect of various salt concentrations (0, 1, 2, 3% NaCl) on the hydrogen peroxide (H2O2) and superoxide anion (O2-) radicals, the activity of superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) has been studied in the leaves of maize (Zea mays L.) plants. High levels of NaCl have been found to lead to an increase in H2O2 and (O2-) content in the leaves. Significant changes in enzymatic activities and isoenzyme contents of SOD and APX were found. Thus, it was observed that the activity of SOD and APO increased at low concentrations (1 and 2% NaCl) of salt and decreased at high (3% NaCl) concentrations. The highest activity of CAT enzymes was detected at 2% and 3% NaCl.