AbstractSince the time a precise role of coenzyme Q10 (CoQ10) in myocardial bioenergetics was established, the involvement of CoQ in the pathophysiology of heart failure was hypothesized. This provided the rationale for numerous clinical trials of CoQ10 as adjunctive treatment for heart failure. A mild hypotensive effect of CoQ was reported in the early years of clinical use of this compound. We review early human and animal studies on the vascular effects of CoQ. We then focus on endothelial dysfunction in type 2 diabetes and the possible impact on this condition of antioxidants and nutritional supplements, and in particular the therapeutic effects of CoQ. The effect of CoQ10 on endothelial dysfunction in ischemic heart disease is also reviewed together with recent data highlighting that treatment with CoQ10 increases extracellular SOD activity.