Carbon nanotubes oxidation has attracted the interest of researchers, because in addition to eliminating impurities, it increases the dispersion of aggregates creating new interactions between materials. In this work, carbon nanotubes (CNT) were treated using two different oxidation methods to determine the effects of each treatment on the surface area of the material. The following methods were used: the traditional chemical treatment (using strong acids) and a treatment supported by microwaves. Results showed that both treatments reduced the surface area (traditional CNT < microwaves CNT < non-treated CNT). By using microwaves, oxidation time was shortened, greater concentration of carboxylic functional groups was obtained and damage to the structure diminished, resulting in oxidized nanotubes with improved structural characteristics.