Bretagne has experimented successfully with CO2 huff ＇n＇ puff injection since 1985 in the Shoemaker field in Kentucky. Numerical simulations were performed with a compositional model to review and to quantify the influence of all parameters that could be responsible for the production improvement observed in the wells. Laboratory studies were conducted to get relevant physical data, particularly concerning relative permeabilities with three phases present. These data were integrated into the numerical model, giving good agreement with field results, and predicted production performance more accurately. Finally, the optimization of the huff ＇n＇ puff process in Shoe-maker is presented.