Coenzyme Q10, a vitamin-like substance, represents a component of the complex antioxidant system of the human organism. The paper presents its structure, physiological function and the role in the disease pathogenesis with the accent on the supplementation therapy during human immune system disturbances, including infectious and oncological diseases.

        Key words: coenzyme Q10, humoral immunity, cellular immunity, antitumorous effect, antiviral effect.