Based on the density functional theory calculations, we predict that the Yttrium-dispersed capped-carbon nanotubes (CCNY) can serve as a high-capacity hydrogen storage material. The interaction of H-2 molecules with the CCNT can be significantly enhanced upon decoration by Y atoms. The H-2 molecules binding to the Y-CCNT system is similar to the Y -C-60 system with a maximum of six H-2 molecules per Y atom and an average binding energy of -0.48 eV, which is suitable for reversible hydrogen storage at ambient conditions. With six Y atoms located, the gravimetric density of the cap is found to be 7.51 wt%, thus exceeding the 6.5 wt% target of the U.S. Department of Energy. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.