Because of its industrial importance, poly(ethylene terephthalate) (PET) has been the subject of numerous studies concerning surface modifications in order to improve its bonding ability. Most of the previously reported surface treatments performed before the metallization provide good dry adhesion of vapour deposited metallic layers. However, food packaging applications also require good wet adhesion and strong oxygen barrier properties. Heat treatments have been found to improve these properties. Hence, the aim of this study was to isolate an efficient heat treatment for the metallized PET films suitable for industrial application. The adhesive performance of aluminized polyester films has been assessed by use of an ultrasonic vibration test.