The selected absorption behavior of sulfur atoms on single wall carbon nanotubes (SWNTs) was studied by the density functional theory (B3LYP/6-31G (d)), in terms of absorption energy and charge transfer. It is found that the adsorption on the caps is energetically preferred in perfect SWNTs; the absorption energy and charge transfer on 5-1DB defects are significantly large with respect to perfect sites on SWNTs, suggesting selective absorption of sulfur on these defects. Importantly, adsorbed sulfur atoms can effectively stabilize these defects through the formation of S-C bond, which is not found in perfect SWNTs. The selective adsorption behavior described above may shed light on the promoting mechanism of sulfur atoms on the production of SWNTs. (c) 2008 Elsevier B.V. All rights reserved.