This review focuses on selected aspects in counter-current gas absorption processes where improvements were made in recent years. In order to put the material into proper perspective, the classical design procedure for counter-current absorption column is briefly reviewed. One of the central issues in gas absorber design is the need for volumetric mass-transfer coefficients, which in a sense reflect the mass transfer performance of the respective packing. Data on gas-phase mass transfer resistance is somewhat more abundant in the literature because it can quite easily be measured during distillation runs at total reflux. This review thus concentrates on the liquid-side mass transfer characteristics of packed columns. In view of the growing importance of structured packings, the mass transfer performance of a typical structured packing receives special attention. The review then discusses recent progress on two very important second order effects, namely heat effects and liquid axial dispersion. It briefly also treats available short-cut design procedures allowing to assess the importance of such effects without resorting to complex numerical computer calculations