Polyphenylquinoxaline (PPQ) and divinylsiloxane bis-benzocyclobutene (BCB) are of great technological interest concerning the fabrication of electronic multilayer devices. Both polymers own similar electrical properties but differ in their adhesion behavior towards copper. Photoelectron spectroscopy utilizing x-ray and ultraviolet radiation has been used to study the electronic structure of the Cu/PPQ and Cu/BCB interfaces. Thin layers of the polymers were produced by spin coating and their surface topologies were examined using atomic force microscopy. The metallization was done by evaporation and the gradual growth of the interface region was examined in situ after every metallization cycle. In both cases a reactive interface region with a low oxygen content is found. The difference in the adhesion between the two systems towards copper is discussed with respect to the differences of the interfaces formed during the metallization.