The absorption of carbon dioxide from a carbon dioxide/nitrogen mixture into an aqueous diethanolamine solution (as an example of a typical amine solution) using a hollow fiber contactor is simulated to obtain the effect of several operational variables (liquid velocity, fiber length, lean carbon dioxide loading and, amine concentration) on productivity and amine solution to carbon dioxide ratio. The model employed is based on the ones commonly used in the literature for this process, but it was significantly improved as some simplifications usually considered (irreversible reaction, low carbon dioxide loading constant partition coefficient of molecular carbon dioxide between liquid and gas phases. absence of bicarbonate and carbonate anions) have been removed. The effect of these simplifications on the simulated results is quite important. A simple performance parameter study is proposed to evaluate the contactor's performance, keeping the feed gas concentration and the fraction of carbon dioxide removal constant. This procedure leads to optimum values of the liquid velocity and lean carbon dioxide loading, while the performance parameter improves with amine concentration. (C) 2009 Elsevier B.V. All rights reserved.