Differently charged liposomes were examined for the efficiency of delivery of Cu/Zn superoxide dismutase (CuZnSOD) to human lung epithelial cells, A2182, and their prospects of cell protection from oxidative agents. A2182 cells were treated with cationic, neutral and anionic liposomes with encapsulated CuZnSOD. Untreated cells and cells pre-treated with liposome-encapsulated CuZnSOD were exposed to oxidative stress caused by xanthine/xanthine oxidase. Cellular antioxidant response was monitored for 4 or 24h after the beginning of oxidative stress induced by the activity of superoxide dismutase (SOD) and total glutathione concentration. CuZnSOD-loaded liposomes increased the SOD activity of A2182 cells 24h after treatment. The highest increase of cellular SOD, by 108%, was achieved using anionic liposomes. Neutral and cationic liposomes increased cellular SOD by 83 and 85%, respectively. Cationic liposomes were the most cytotoxic. Exposure of untreated cells to oxidative stress increased the cellular glutathione level after 24h. Cells pre-treated with liposome-encapsulated CuZnSOD were protected from oxidative stress, as shown by the unchanged concentration of cellular glutathione.