Density functional calculations have been carried out to investigate the interaction of hydrogen molecules with Li-doped charged single-walled carbon nanotubes (SWNTs). The results show that binding of H(2) on positively charged Li-doped SWNTs is enhanced compared with that on uncharged systems. As the charge of the Li-doped SWNTs increases, the binding energy of H(2) increases with the largest binding energy of 0.26 eV. The reason for the increase in H(2) binding energy is that the positively charged tube improves the charge transfer from Li atom to the tube and make the Li atom more ionized, which strengthens the polarization interaction between H(2) and Li atom. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.