The metal complex effect on the hydrogenation of m-chloronitrobenzene: and p-chloronitrobenzene (CNB) over poly-vinylpyrrolidone-stabilized platinum colloidal catalysts (PVP-Pt) has been studied under 303 K and atmospheric pressure. The introduction of metal complexes to the catalytic system has great effect on the activity and the selectivity of the catalyst. On the addition of the complexes Co(AcAc)(3)(-) and Ni(en)(3)(2+) to the hydrogenation of m-CNB, the selectivities to m-chloroaniline (CAN) were increased from 82.2% to 95.5% and > 99.9%, while the activities were 0.88 and 0.18 mol H-2/mol Pt s (the neat PVP-Pt catalyst with 0.69 mol H-2/mol Pt s), respectively. With iron(III) 8-hydroxyquinoline (8-HQ) complex Fe(8-HQ)(2+) as a modifier, the highest selectivity of p-CNB to p-CAN(> 99.9%) was obtained, even though its activity was decreased from 1.11 to 0.56 mol H-2/mol Pt s.