Elevated CO2 concentration (700 cm3 m-3, EC) inhibited chill-dependent (7 °C) depression of net photosynthetic rate of two maize hybrids with different sensitivity to low temperature. The rate of superoxide radical formation in leaves, leaf membrane injury, and the decrease in maximal quantum efficiency of photosystem 2 were successfully diminished by the treatment. The protective effect of EC toward stress conditions was prolonged at the recovery phase (20 °C). The genotypic impact on studied parameters was also notable. and R. Bączek-Kwinta, J. Kościelniak.