The activated carbon obtained by chemical activation of peach stones with KOH has been modified by H2O2, (NH4)(2)S2O8, HNO3, CH3COOOH (peroxyacetic acid), air, NH3, H-2 or by thermal treatment to change the character of its surface by introduction or removal of oxygen functional groups. The modified activated carbon samples obtained have been subjected to elemental analysis, TPD measurements and texture characterisation. In all samples the dominant presence of micropores has been established and they have been found to differ much in the content of oxygen groups. The catalytic properties of the carbon samples in the reaction of oxidative dehydrogenation of isobutane to isobutene (ODI) have been studied. All the samples have been shown to catalyse the ODI reaction whose optimum temperature is in the range 523-673 K. The isobutene yield values obtained are close to those reported by other authors, and they have been found to depend not only on the content of oxygen in a given carbon sample but also on the type of oxygen functional groups. The results seem to confirm the hypothesis that the carbonyl/quinone groups are the active sites involved in ODI. (C) 2009 Elsevier B.V. All rights reserved.