Resistance to oxidative damage is an important feature of cancer cells. Cellular anti-radical enzymes, lipid peroxidation, glutathione pathway, capability to produce ROS, and cells' susceptibility to H2O2 and menadione toxicity, were analyzed in DND-1A and HeLa cancer cell lines. SOD and GSHPx activities were higher in DND-1A than in HeLa cells. Lipid peroxidation was the same in both cell lines, while menadione stimulation of ROS production was tenfold higher in HeLa cells. Total and reduced, but not oxidized, glutathione levels, were tenfold smaller in HeLa cells. H2O2 proved fatal to HeLa cells after 12 hours' incubation, while it was ineffective on DND-1A; DND-1A cells were more sensitive to menadione toxicity than HeLa cells. The two lines behaved differently in response to the above treatments. These observations might be important in designing more specific cancer treatments.