A series of unsupported dimolybdenum nitride (gamma-Mo2N) catalysts differing in surface area were prepared by temperature programmed reduction of MoO3 with a mixture of NH3:N-2 (90:10). Characterization of catalysts by BET, XRD, TPR and XPS techniques was carried out. The samples were used as catalysts in hydrotreating reactions (simultaneous hydrodesulfurization of thiophene and hydrogenation of cyclohexene). Low surface area gamma-Mo2N materials show much higher specific conversions than those with higher surface area. These results indicate that HDS and HYD reactions over gamma-Mo2N seem to be structure-sensitive. The relative exposure extent of crystalline planes (111) and (200) over the different catalysts can be associated with their hydrogen adsorption capacities and with their catalytic performances. The catalytic activities are significantly affected by the catalyst pretreatment conditions.