Pd black was deposited on a cation or anion exchange membrane by electroless plating and the subsequent electroplating. Total amount of Pd black deposited on the ion exchange membranes was about one eighth of the mass of the corresponding Pd sheet used in the previous work. A hydrogenation system of styrene and a dechlorination system of 4-chlorotoluene were successfully constructed using a two-compartment cell separated by the resulting palladized ion exchange membranes. The sole hydrogenation product was ethylbenzene, and the dechlorination product was only toluene. In each case current efficiency for ethylbenzene and toluene production was markedly improved by using methanol with high polarity and was not less than that on a Pd sheet or palladized one as a reference. Considering these results, the plausible mechanism of the hydrogenation and dechlorination on the palladized ion exchange membranes was discussed. (C) 2003 The Electrochemical Society.