The effects of bromine treatment on the properties of multi-walled carbon nanotubes (MWCNTs) such as surface porosity, sp(2) hybridization, functional groups and hydrogen storage capacity were studied and compared with treated MWCNTs by HCl, HNO(3) and H(2)SO(4) acids. The treatments affect the graphitization properties (sp(2) hybridization) and porous structures of MWCNTs by enlarging the specific surface area and the micro-pore volume. In addition, the hydrogen storage capacity of the treated MWCNTs was also investigated by volumetric technique. It is found that the destroying of sp(2) hybridization of bromine treated MWCNTs increases hydrogen adsorption sites and decreases hydrogen desorption temperature. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.