Hydrocracking reactions of di(1-naphthyl)methane (DNM) and hydrogenated di(1-naphthyl)methanes (H-DNMs) were investigated at 300 degreesC to examine the relationship between structure and reactivity of the substrates. The results show that in the presence of Ni-S DNM is readily hydrocracked to naphthalene and 1-methylnaphthalene under pressurized hydrogen, while the more deeply DNM is hydrogenated, the more slowly the resulting H-DNMs are hydrocracked. The differences between DNM and H-DNMs and among the different H-DNMs in reactivity toward hydrocracking can be ascribed to the hydrogen-accepting abilities of ipso-carbons in the substrates, the stabilities of leaving arylmethyl radicals and the adsorption strength of the substrates on catalyst surface.