This paper highlights the importance of operating and design parameters to mass-transfer in CO 2 absorption in columns with structured packings. The study compares the performance of four stainless steel packings, Gempak 4A, Mellapak 500Y, Mellapak 500X, and Optiflow. Mass-transfer efficiency of these packings was determined by carrying out absorption experiments in a pilot-scale absorption unit with aqueous solutions of sodium hydroxide (NaOH) and monoethanolamine (MEA) as test liquid. The overall mass-transfer coefficients (K G a e ) were calculated from experimentally determined gas-phase CO 2 concentration profiles within the test columns. The results of this study indicate that mass-transfer coefficient of these structured packings tested varies significantly not only with operating parameters such as liquid load, liquid CO 2 loading and liquid temperature but also with design parameters, i.e. the pattern of packing arrangement and initial liquid distribution.