Gas-liquid membrane contactors are promising alternatives to conventional absorption technologies. However, in spite of their important advantages, such systems suffer from gradual wetting of porous membranes with liquid absorbents. This review focuses on the wetting phenomenon, which is the main concern for long-term operation of CO2 absorption in membrane contactors and has therefore an important impact On industrial applications. The impact of membrane wetting on mass transfer resistance and absorption efficiency, the effect of influencing parameters including absorbent (operational conditions, type and concentration) and membrane (hydrophobicity, pore size and porosity) properties on wetting phenomenon, as well as different methods to prevent membrane wetting, along with their advantages and drawbacks are discussed in detail. (C) 2013 Elsevier B.V. All rights reserved.