This paper reviews wash systems for conditioning (removal of CO//2 and H//2S) of natural and industrial gases, and provides recommendations for selection criteria. It is shown that the selection of a proper wash system among the many systems available becomes more and more difficult. The first decision between a physical and a chemical system may still be relatively straightforward. The final selection, however, requires very detailed information from the client and a well established know-how on the plant supplier's side. With a physical wash, the integration of the system into the overall process scheme and the adaptation to the various battery limits conditions is especially important.