Hormonal system status has been analyzed in leaf disks of hypersensitive tobacco Nicotiana tabacum L. variety Samsun NN during the development of resistance to tobacco mosaic virus (TMV) induced by synthetic coenzyme Q₁₀ (ubiquinone 50). The absolute and relative content of abscisic acid (ABA), indoleacetic acid (IAA), and cytokinins (CKs) was determined after the exposure of leaves to Q₁₀ solution and the subsequent TMV infection. In plants not treated with Q₁₀, CK content increased about 2.5 times 1 day after TMV infection, while a significant increase in the ABA level and a decrease in the IAA level were observed only after 2 days. In the dynamics, Q₁₀ treatment had a protective antiviral effect, significantly decreased the ABA level, and increased the IAA level in sensitized plants compared to nonsensitized ones.