The coenzyme Q10 (ubiquinone) plays an important role in bioenergetic conditions in myocardiac cells and together with alpha-tocopherol they act as endogenous antioxidants. Decreased levels in coenzyme Q10 were confirmed in some types of cardiomyopathies and in failing myocardium. Insufficiency of E vitamin is a risk factor in cardiovascular diseases. The study investigates the levels of coenzyme Q10 and alpha-tocopherol in the blood and in bioptic samples of the myocardium in patients with cardiopathies of unknown origin and it is aimed at their application as an auxiliary diagnostic method. The authors have introduced a method of coenzyme Q10 and alpha-tocopherol assessment from the bioptic samples of the myocardium, from the blood and plasma of these patients by means of high-performance liquid chromatography (HPLC). The authors detected decreased levels of coenzyme Q10 in the myocardium and blood of patients with cardiopathies. The dependence on the functional state of the myocardium according to NYHA was not confirmed due to the small number of patients. The plasmatic alpha-tocopherol levels decreased in dependence on the severeness of the disease. A more significant dependence was detected between the levels of alpha-tocopherol in the myocardium and its functional state. The average myocardial level of alpha-tocopherol in patients of the NYHA II group was almost ten-fold higher than in the NYHA II group. The gained results appoint to the meaning of investigation of the coenzyme Q10 and alpha-tocopherol in patients with cardiopathies of unknown origin and give a hint of prospective possibilities for application in the diagnosis assessment.