Activated carbon fibres (ACFs) have been successfully prepared with a remarkable development of porosity from four isotropic coal tar pitches and four isotropic petroleum pitches. Special care has been put to make the activation process at similar activation rate in order to have a better comparison of the different precursors used. The micropore volumes of petroleum pitches-derived ACFs are higher than those obtained from coal tar pitches under similar activation yields. The resultant ACFs present interesting textural properties: they are essentially microporous materials, with a high adsorption capacity which increases linearly with the burn-off. It has been observed, independently of the pitch precursor used, that the micropore volume is a function of the degree of activation, being, in all the cases, quite similar for a given activation degree if a comprehensive weight loss is considered (carbonization lost and degree of activation). ; MEC and FEDER (CTQ2006-08958) and GV (GV/2007/144 and ARVIV/2007/063).