Single-walled carbon nanotubes (SWNTs) have been synthesized by the pyrolysis of methane using hydrogen decrepitated Mischmetal (Mm) based AB(3) alloy hydride catalyst by catalytic chemical vapour deposition (CCVD) technique. The use of metal hydrides as catalysts for the bulk synthesis of good quality SWNTs by CCVD technique has been demonstrated. Nanocrystalline Pt dispersed single-walled carbon nanotubes (Pt/SWNT) have been prepared by chemical reduction method using functionalized SWNT. SWNTs and Pt/SWNTs have been characterized by SEM, TEM, HRTEM, Raman, TGA and XRD studies. Hydrogen storage properties of as-grown, purified SWNT and nanocrystalline Pt dispersed SWNT have been investigated using high-pressure Seiverts' apparatus in the pressure range 1-100bar and at 298 and 125K. The effects of purification and dispersion of Pt nanoparticles on the hydrogen storage capacity have been discussed based on the chemisorption process. (C) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.