The influence of hydrothermal treatment on the structural and textural properties of Ni/gamma-Al(2)O(3) catalysts is investigated by means of X-ray diffraction (XRD), H(2)-TPR, TG-DSC and N(2) physisorption. After hydrothermally treated at 90-150 degrees C and 8-48 h, the gamma-Al(2)O(3) support transforms into its hydrated phase, boehmite [gamma-AlO(OH)]. And the content of gamma-AlO(OH) increases with the hydrothermal temperature and time increasing. Furthermore, the hydration of gamma-Al(2)O(3) support induces the aggregation of carried Ni crystallite and decreases the BET specific surface area and pore volume, and also reduces the interaction between Ni and gamma-Al(2)O(3) support. The above structural and textural changes further cause the hydrogenation activity decay of Ni/gamma-Al(2)O(3) catalyst. (C) 2010 Elsevier B.V. All rights reserved.