In this study, we investigated the antioxidant activity of hesperidin and hesperetin, which are the active compounds from Citrus junos, in the cellular system. Under cellular model of oxidative damage using LLC-PK 1 renal epithelial cell, the oxidative damage induced by 2,2-azobis (2-amidinopropane) dihydrochloride (AAPH) led to the loss of cell viability, while treatment of hesperidin and hesperetin increased significantly the cell viability as dose-dependent manner. In addition, NO-induced cellular oxidative damage by sodium nitroprusside were significantly recovered by the treatment of hesperidin and hesperetin, showing the increase of cell viability. But hesperidin and hesperetin showed no significant protective effect on O 2 - -induced cellular oxidative damage. The present study indicates that hesperidin and hesperetin protect against free radical, especially AAPH-induced peroxyl radical. In particular, hesperetin has stronger protective effect against oxidative stress than hesperidin.