The structural effect on the rate of CO2 reduction was studied with voltammetry on single crystals of Pd (Pd(111), Pd(100), Pd(110)) in 0.1 M HClO4 saturated with CO2. CO2 was reduced to an adsorbed product at potentials more negative than -0.1 V vs. RHE. The rate of CO2 reduction depends remarkably on the crystal orientation : Pd(100) < Pd(lll) < Pd(110). The Pd(111) surface shows uniquely high activity, whereas (111) is the surface of lowest activity in CO2 reduction for other Pt group metals (Pt, Ph, Ir). The rate of CO2 reduction at -0.5 V vs. RHE on Pd(110) is two orders of magnitude higher than that of Pt(110).