A physical method and a chemical method have been used to determine the mass transfer performance of structured packing for gas-liquid absorption under co-current downward operation. The results show firstly that gas-side resistance is negligible, secondly that the minimum liquid load to achieve full wetting of the packing is about 150m(3)/m(2)/h, and lastly that the Higbie theory gives values of liquid side mass transfer coefficient in good agreement with the experimental data provided that the exposure time is based on liquid film's characteristics. (C) 2004 Elsevier Ltd. All rights reserved.