The formation of various fullerenyl radicals during the polymerization of methyl methacrylate (MMA) and styrene in the presence of C 60 fullerene is studied using the density functional method. It is shown that the interaction of an initiating radical with the fullerene molecule, yielding fullerenyl radical, is less favorable in energy terms than the initiation of the chain, i.e., the interaction of the same radical with a monomer. For radical polymerization of styrene, the termination of polystyrene chains on the fullerene is thermodynamically more probable than the growth of polystyrene chains, with the reactions being equiprobable in the case of MMA polymerization. The addition of monomer molecules to fullerenyl radicals is characterized by an enthalpy of activation exceeding that for conventional free radical chain growth by no more than 1.4 to 2.3 times; the thus formed growth radicals with fullerene molecules incorporated into the backbone polymer feature a reactivity not inferior to conventional polymer growth radicals.