Thermoanalytical (TG, DTG) and adsorption methods were applied in investigation of waste agricultural products, e.g. plum stones, which can serve as raw materials for production of active carbon. The study was performed on three series of carbonaceous materials prepared from plum stones. In the first series, the raw material was subjected to ammoxidation by a mixture of NH3/air, carbonisation and activation by steam. In the second series, the material was carbonised, ammoxidised and activated with steam, whereas in the third series, it was carbonised and finally activated. Modification of carbonaceous material by ammoxidation was used in order to obtain carrier material for catalysts with diverse surface properties. The above procedure allows obtaining an active carbon precursor with high density of surface nitrogen sites of Lewis basic character, which may play an important role as active sites in the catalytic processes. (C) 2005 Published by Elsevier B.V.