Fifteen configurations and adsorption energies of the adsorption sites of BH3∙∙∙HCN on Co(100) and Co(110) surfaces were investigated using the density functional theory. The results show that after BH3∙∙∙HCN is adsorbed, although there is no general behavior for the H∙∙∙H distances, the adsorption energies of BH3∙∙∙HCN are always far stronger than those of H2 on Co surfaces, suggesting that the dihydrogen-bonded complex, one kind of prospective material for reversible hydrogen storage, can be tightly adsorbed on the surfaces of metals. Thus, the attempts to store the significant amounts of H2 can be successful by the way that the dihydrogen-bonded complexes are adsorbed on the surfaces of metals. The stability and binding mechanism was analyzed by the Mulliken charge population and reduced density gradients (RDGs) methods.