Selective oxidation of single-wall carbon nanotubes (SWCNTs) by H2O2 was conducted at varying heating times and monitored by UV-vis-NIR spectroscopy. A major increase in the relative absorption intensity indicated a higher than 80% concentration of metallic SWCNTs in the final product. Here, it is suggested that semiconducting SWCNTs are more reactive than metallic SWCNTs because of hole-doping by H2O2, resulting in faster oxidation.