The hydrogenation of m-dinitrobenzene to m-phenylenediamine in liquid phase was studied with the platinum catalysts supported on TiO2, Al2O3 and TiO2-Al2O3 carriers. These materials were successfully activated either by simple in situ reduction technique that makes use of the same reaction conditions or conventional reduction with H2 flowing at 723K. Among the catalysts tested, the Pt/TiO2-Al2O3 catalyst showed the highest activity and selectivity towards m-phenylenediamine, over which 99% m-dinitrobenzene conversion and 97% m-phenylenediamine selectivity were obtained at 363K under hydrogen pressure of 8,1 MPa after reaction for 22 h when using ethanol as solvent and the catalyst was previously activated by the in situ activation method. Keywords: m-dinitrobenzene, m-phenylenediamine, Catalytic hydrogenation, Supported Pt, Activation method.