The production of activated carbons derived from waste tires has been carried out using steam and carbon dioxide as activation agents. The effect of temperature and activation time over the carbons prepared has been studied. The material subjected to activation has been char or residual carbon black obtained by continuous flash pyrolysis of waste tires carried out in a conical spouted bed reactor at 500 °C. The activation has been carried out at 850 and 900 °C using steam and only at 900 °C using carbon dioxide due to the slower kinetics of this process. The activation runs have been conducted in a fixed bed reactor. An essentially mesoporous structure is developed in the process, with BET surface areas above 500 m2/g for the carbons obtained with steam and above 370 m2/g in those obtained using carbon dioxide.