In industrial applications CO2 is frequently removed from gas streams at elevated pressures by absorption and subsequent chemical reaction in carbonate/bicarbonate solutions (e.g. Benfield process). The criterion that determines whether or not this reaction can be regarded as pseudo-first order is given by Danckwerts and Sharma (1966), but its derivation has never been published. In the present study, a consistent set of equations and physico-chemical parameters is presented to describe the CO2 absorption/reaction process. It was found that the criterion was justified, but should be somewhat confined to reduce possible errors. Furthermore, the model was validated by experiments in a stirred cell reactor up to CO2 partial pressures of 16 bar. (c) 2005 Elsevier Ltd. All rights reserved.