The influence of thermal stabilizers on the poly(s-caprolactone) (PCL) diffusion in poly(viny1 chloride) (PVC)/PCL blends was studied with the addition of various concentrations of dibasic lead phthalate and dibutyltin dilaurate. The rate of PCL diffusion was followed by differential scanning calorimetry and IR spectroscopy in three series of experiments: the migration of PCL at the surface of the sample; the extraction of PCL in a fluid surrounding the sample; and the sorption of liquid PCL in the blend. In the last two series, mass losses and mass uptakes were measured as a function of time. As compared to the blend without additive, dibutyltin dilaurate induces an increase of the PCL rate of diffusion whereas dibasic lead phthalate gives a decrease. These trends are explained by: first, the formation of an associative complex between dibutyltin dilaurate and PVC, which can compete with the PVC/PCL interactions in the blend and thus favor the PCL migration; and, second, the modification of the T, of the blend induced by the addition of a third component, which can modify the diffusion rate by changing the free volume fraction at the diffusion temperature. T, decreases slightly in the presence of dibutyltin dilaurate but increases with dibasic lead phthalate.