Searching for better adhesion properties of metallic thin films to polymer substrates, we have studied the influence of the plasma and thermal treatments of poly(paraphenylene-vinylene) thin films on their adhesion to aluminum layers. The adhesion was found to be substantially increased when the polymer surface was treated with oxygen by RF sputtering, or when it was kept at high temperature prior to the metal deposition. An attempt has been made to explain the adhesion improvement in terms of surface analysis (XPS) and scanning electron microscopy (SEM) results of the treated surfaces. Both the metal-oxygen-carbon complex formation at the interface and the roughness induced by the oxygen treatment were found to be the reasons for the improved adhesion properties.