The stoichiometric factors of inhibition and the rate constants (k7) were measured for the reaction of isobornylphenols with peroxy radicals of ethylbenzene. The values of k7 of the compounds under study increase with an increase in the amount of alkyl substituents and OH groups on the aromatic ring. The introduction of the oxygen atom between the o-isobornyl substituent and the aromatic ring decreases k7 by a factor of 6.5. The inhibiting action of binary mixtures of sterically hindered phenols with 2-isobornyl-4-methylphenol and 2,6-diisobornyl-4-methylphenol in the initiated oxidation of ethylbenzene is close to additive.