The aim of this study was to examine the protective and/or mitigative properties of resveratrol (RSV) administered before or after irradiation of human lymphocytes in vitro. The isolated lymphocytes were incubated for 1 h with resveratrol, at doses of 0.1 (lowest), 0.5 (medium) or 1 (highest) mM/ml: 1 h before; immediately before; immediately after irradiation; and 1 h after irradiation with 0.5, 1 and 2 Gy. The degree of DNA damage was evaluated by Comet Assay. Treatment of human lymphocytes with resveratrol 1 h before or immediately after radiation exposure showed protection from radiation-induced DNA damage. However, 1 Gy irradiation + 1 mM/ml RSV, and 2 Gy irradiation + 0.5 and 1 mM/ml RSV 1 h before irradiation did not provide the same protection. Significant dose-dependent reduction of the level of DNA damage was observed after application of RSV immediately postirradiation or 1 h postirradiation. The reduction in DNA damage was the highest at the 0.1 dose of resveratrol. Our results lead to the conclusion that resveratrol may act both as a radioprotector as well as a radiomitigator. Resveratrol at the lowest (0.5 mM/ml) dose was more effective when combined with 0.5 and 1 Gy doses of radiation.