The structure and catalytic properties of Pd catalyst supported on the outer surface or inner surface of carbon nanotubes (CNTs) have been investigated by using various experimental techniques combined with acetylene selective hydrogenation tests. It has been shown that Pd/CNTs-out catalyst exhibits higher ethylene selectivity than Pd/CNTs-in catalyst for acetylene selective hydrogenation. The electron interaction between CNTs support and palladium particles is responsible for higher ethylene selectivity over Pd/CNTs-out catalyst. It is found that Pd/CNTs-out catalyst exhibits higher ethylene selectivity than Pd/CNTs-in catalyst for acetylene selective hydrogenation. The electron interaction between CNTs support and palladium particles is responsible for higher ethylene selectivity over Pd/CNTs-out catalyst.