Electronic structures and band gaps of hydrogenated fullerenes have been investigated by means of density functional theory method. The mechanism of hydrogen addition reaction to the fullerene (C-60) surface was also investigated. Addition of one and two hydrogen atoms was examined in the calculations. The binding energies of the second hydrogen atom to C60H were widely distributed in the range 1.5-3.6 eV. It was found that the bonding energy is strongly dependent on the spin density of carbon atom of C60H. The second hydrogen atom preferentially binds to the neighbor site of the first addition site. The electronic states and excitation energies of C-60-H were discussed on the basis of theoretical results. (C) 2013 Elsevier B.V. All rights reserved.