Stability and hydrogen storage properties of various metal-decorated benzene complexes have been studied using a first-principles method. According to our results, most metals from the first to the third period of the periodic table can be strongly adsorbed on the benzene surfaces, except Be, Na, Mg, K, and Zn. Among the metals we studied Ca is the most promising adsorbate for hydrogen storage. Two Ca atoms prefer to be isolated on the benzene surfaces, one on each side, and each adsorbed Ca can adsorb up to four H-2 molecules, thus yielding a H-2 uptake of 9.2 wt%. The calculated binding energy is 0.45 eV/H-2, suitable for reversible hydrogen storage. The adsorbed Li and Sc can also adsorb a large number of H-2 molecules with suitable H-2 binding energies, but they are likely to dimerize on the benzene surfaces. Other metal adsorbates we studied are not suitable for hydrogen storage, because they will suffer from the large H-2 binding energy or the low hydrogen storage capacity. (C) 2012 Elsevier B.V. All rights reserved.