The gas-phase maleic anhydride hydrogenation was studied at 170 A degrees C and 1 bar using Ni/SiO2-Al2O3 catalysts varying metal loading. The maximum gamma-butyrolactone selectivity was reached for a 10 wt% nickel load. On the basis of temperature programmed experiments, it is proposed that new active sites in selective succinic anhydride hydrogenolysis are formed when Ni loads are higher than 8 wt%.