The aim of this work was to characterise hydrodynamics and mass transfer in a gas-liquid contactor containing static mixers (SMs). The originality of this study lies in the fact that these mixing organs are used with a gas continuous phase. Two types of SM were implemented in co-current flows, Statiflo and Lightnin. The pressure drop Delta P, the volumic interfacial area a and the volumic mass transfer coefficient k(L)a were measured in several configurations: horizontal flow, vertical up-flow and vertical down-flow. The influences of position and flow rates were studied in order to understand the behaviour of these contactors, and to optimise the operating conditions. As expected, the pressure drop was found to increase mainly with gas velocity but also with liquid velocity, and to reach 3300Pa in the range of velocities studied (the gas flow rate varied between 4 and 30 m(3)/h and the liquid flow rate between 0 and 100 L/h), far less than Sulzer SM. The volumic interfacial area and the volumic mass transfer coefficient showed the same changes, a varying between 100 and 1000 m(2)/m(3), and kLa reaching 0.07 L/s. This is interesting compared with other classical absorption processes: indeed, even if packing towers can provide the same range of values, the operating conditions are more drastic or the dimensions of the apparatuses are far larger than SM ones. The position was also found to have an influence on the hydrodynamic and mass transfer parameters (Delta P, a and k(L)a). (c) 2005 Elsevier Ltd. All rights reserved.