When single-wall carbon nanotubes (SWNT) were treated with H2O2, rates of SWNT oxidative-degradation were found to be enhanced with irradiation of light. Raman spectroscopic study indicated that, when the irradiation periods were 2 and 5 min, the radial breathing modes of SWNTs having gap energies corresponding to the wavelength of the irradiated light selectively disappeared. This result suggests that SWNTs having a gap energy corresponding to the wavelength of the irradiated light were preferentially removed. (C) 2003 Elsevier Science B.V. All rights reserved.