This paper deals with a study on mass transfer in modular catalytic structured packing Katapak-SP with the purpose of determining the effective mass transfer area. Information has been gathered by using the chemical absorption method and monitoring the composition profiles along the packed bed. Liquid load ranged between 5 and 27 m3/(m2h). A procedure was developed taking into account the hybrid structure of the packing. The use of correlations for the volumetric mass transfer coefficient available in the literature and of data obtained from targeted experiments allowed chosing the proper operating conditions. A simple model to calculate the effective area is presented. The model is based on the packing geometry and the liquid flow distribution within the hybrid structure of the packing.