Selectivity difference between hydrogenation of acetophenone over carbon nanotubes (CNTs) and commercial activated carbons (ACs) supported Pd catalysts has been investigated. The selectivity of alpha-phenylethanol over the Pd/CNTs catalyst is significantly higher than that over the Pd/ACs. The optimal yield of a-phenylethanol over the Pd/CNTs catalyst is 94.2% at 333 K under atmospheric H(2) pressure for 255 mm, but it is only 47.9% over the Pd/ACs catalyst. HRTEM characterization and density functional theory (DFT) study of the two catalysts suggested that the defects of the carbon support are the main anchoring sites for Pd nanoparticles. Additionally, mechanistic study of the acetophenone hydrogenation over the two catalysts suggested that the different adsorption modes of reaction intermediates (products) on the two kinds carbon supported Pd nanoparticles are responsible for the dramatic selectivity difference. (C) 2011 Elsevier B.V. All rights reserved.