The electronic structures and the hydrogenation of a chiral single-wall (6,4) carbon nanotube have been investigated by density functional theory. Our results indicate that, along the long vector of the tube, the HOMO and LUMO exhibit well-regulated arrangement of the bonding and anti-bonding structures. The adsorption of odd hydrogen atoms on the tube leads to obvious deformations of the tubular structure and the hydrogenation of the (6,4) tube can be well predicted by examining the topology of HOMO. (c) 2005 Elsevier B.V. All rights reserved.