Hydrogen storage properties of 10 different adatom decorated silicene are carried out using density functional theory calculations with long-range van der Waals dispersion correction. It is found that the binding energy between metal adatoms and the silicene is greater than the cohesive energy of bulk metal so that clustering of adatom will not occur once it is bonded with silicene. The adsorption of H-2 on Li, Na, K, Mg, Ca, and Au decorated silicene is a weak physisorption. Differently, a weaker chemisorption is responsible for the adsorption of H-2 on Be, Sc, Ti, and V decorated silicene. In particular, silicene with Na, K, Mg, and Ca decorating on both sides leads to 7.31-9.40 wt% hydrogen storage capacity with desirable adsorption energy, indicating that the metal-decorated silicene can serve as a high capacity hydrogen storage medium. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.