The cocurrent downflow contactor reactor (CDCR) has been found to give low mass transfer resistances both in slurry and packed bed catalytic operation. The hydrogenation of propan-2-ol solutions of itaconic acid in the range 100-300 kPa and 20-70 degrees C and of soyabean oil in the range 100-500 kPa and 130-160 degrees C was studied using slurry (5% w/w Pd/C) and packed bed (3% w/w Pd/Al2O3 Raschig ring) catalyst. Mass transport and kinetic parameters were evaluated for both operational modes and while the slurry CDCR gave better mass transfer properties than the packed bed CDCR, the latter gave better mass transfer than conventional reactors and superior selectivity to the slurry CDCR. As has been observed with the slurry CDCR, the packed bed CDCR was found to operate under surface reaction rate control with negligible transport resistances. This was particularly evident for soyabean oil hydrogenation, which is well known to be transport controlled in conventional reactors.