Cryptoquinone, an abietane-type diterpene para-quinone from the bark of Cryptomeria japonica has antifungal and cytotoxic activities, but its biological actions are largely unknown. In this study, we found that para-hydroquinone derivatives inhibited adipocyte differentiation. The actions might have been mediated, at least in part, by activation of the antioxidant-response element induction of phase 2 enzymes and increases in total glutathione.