Coenzyme Q (CoQ), a lipophilic substituted benzoquinone, is well known as a redox component of the mitochondrial and many bacterial respiratory chains. However, additional locations and roles have been recently discovered. CoQ is described as a redox component of extramitochondrial electron transport chains and it is a powerful antioxidant and a membrane stabilizer. Increasing evidence for the beneficial clinical effects of CoQ administration in senescence or in different disorders (e.g. cerebrovascular, muscular, neurogenic) may be explained by the multiple roles of CoQ in cells.