The mitochondrial component coenzyme Q10 (CoQ10) has been used for many years as a dietary supplement intended to promote good health by trapping free radicals, thus preventing lipid peroxidation and DNA damage. We have tested its use as a generic anti-apoptotic compound and have found that its ability to protect against apoptosis varies depending on both cell type and mode of cell death induction. We have further established that this protection may be mediated by its effect on mitochondrial function and viability. We provide additional evidence that CoQ10's protective effect on mitochondrial membrane potential does not always result in altered mitochondrial enzyme activity and neither does it guarantee survival. These observations open the way for further investigations into the mechanisms involved in mitochondrial control of apoptosis.