In this study, we employed density functional theory to investigate the adsorption mechanisms of O-3 on the sidewalls of C(5,5), C(8,8), and C(10,0) single-wall carbon nanotubes (SWCNTs), also having Stone-Wales (SW) defects with different orientations. An understanding of the adsorption of O-3 on SWCNT sidewalls with SW defects was obtained by examining local structural changes, described by the pyramid alization angle, while in investigating the electronic structure of ozonized SWCNT, the results were found to be consistent with experimental observations in some cases. (C) 2007 Published by Elsevier B.V.