Beech wood xylan, as a model substance for hemicellulose contained in plant biomass waste, was subjected to thermohydrolysis in subcritical water. The composition of the product fractions obtained as a result of its hydrothermal decomposition was studied: the water fraction, the oil fraction and the solid fraction of charred post-reaction residue. An increase in temperature favors xylan thermohydrolysis, leading to the production of saccharides - the products of its hydrolytic depolymerization. The yield of the saccharides contained in the water-soluble product fraction reaches it maximum value at 220 degrees C and 235 degrees C, with the retention time of 0 min. Both extending reaction time up to 30 min and further increasing the temperature favor the occurring of secondary reactions - saccharide decomposition - leading to the production, among others, of carboxylic acids, furfurals and aldehydes, and their further carbonization and gasification. (C) 2011 Elsevier Ltd. All rights reserved.