Electrochemical hydrogen storage in an Ag-CNT electrode has been studied by XRD and Raman spectrum before and after hydrogenation. For purifying the CNTs, acidic and thermal methods have been employed. The presence of a clear RBM mode in the purified sample's Raman spectrum at 238cm(-1) shows that a significant fraction of the CNTs are SWCNTs with an average diameter of about 1.02nm. The amount of stored hydrogen in the electrode is measured during the discharge leg after each cycle of charge/discharge process and the optimum value is about 200 mA h/g (after 10 cycles). As the hydrogen absorption in a pure silver electrode is very little, the enhancement in the discharge capacity is attributed to the CNTs. XRD spectrum of the hydrogenated electrode shows two noticeable peaks at 2 Theta = 33 degrees and 53 degrees, which indicates a new long range ordering process. (c) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.