Dietary antioxidants such as carotenoids, tocopherols, vitamin C or flavonoids exhibit biological activities that are not directly related to their antioxidant properties. The parent compounds and/or their metabolites have impact on cellular signaling pathways, influence the expression of certain genes or act as inhibitors of regulatory enzymes. Thus, they reveal additional biological effects which might be of importance in context with the prevention of degenerative diseases related to the consumption of a diet rich in antioxidants. This review focuses on known non-antioxidant properties of carotenoids, including retinoid-dependent signaling, stimulation of gap junctional communications, impact on the regulation of cell growth and induction of detoxifying enzymes, such as cytochrome P450-dependent monooxygenases.