Diphenylmethane (DPM), 9-benzylphenanthrene (BP), di(1-naphthyl)methane (DNM), 1,2-di(1-naphthyl)ethane (DNE), and 9-(1-naphthyl)phenanthrylmethane (NPM) were used as substrates and hydrogen-transfer reactions from molecular hydrogen to the substrates were examined over an activated carbon (AC) under pressurized hydrogen at 300 degreesC. The results show that the AC catalyzes monatomic hydrogen transfer to the substrates and that the reactivities of the substrates toward hydrocracking decrease in the following order: NPM > DNM > BP much greater than DNE much greater than DPM. These results can be interpreted by the differences in the hydrogen-accepting abilities of the ipso-carbons and the resonance stabilities of the leaving radicals.