Not only catalyst composition, but also temperature, pressure and H-2/C-4 ratio play important roles in vapour phase hydrogenation of maleic anhydride (MA) to gamma-butyrolactone (GBL), affecting both MA conversion and GBL yield. Pressure determines the GBL <-> BDO equilibrium (notwithstanding the presence of excess hydrogen), the H-2/C-4 ratio affects catalyst activity and life, and the optimum reaction temperature depends considerably on catalyst composition. On the contrary, high temperature activation and regeneration by thermal desorption under high hydrogen flow do not show any advantages. Furthermore, by comparing the catalytic reactivity of MA, succinic anhydride (SA) and their dimethyl-esters (DMM and DMS), it was shown that MA may be considered an actual alternative to ester hydrogenation in GBL production. Low conversion was observed with SA/GBL solution and attributed to a competitive adsorption of GBL on the active sites of the catalyst.