The charge transfer of C 2+ ions in collision with the OH radical has been studied theoretically by means of ab initio quantum chemistry molecular methods followed by a semiclassical dynamical treatment. In this first step, only the linear approach has been investigated, taking account of the influence of the variation of the distance r OH of the target during the process. The total and partial cross-sections have been determined, and an evaluation of the cross-sections on the different vibration levels has been performed.