The effect of ozone gas treatment on the adhesion between low-density polyethylene (LDPE) and cellulose was investigated. The ozone treatment of LDPE resulted in a significant increase in the interfacial shear strength as measured by the single fiber fragmentation test, whereas the ozone treatment of cellulose was not successful in improving the adhesion. An extensive surface characterization was performed to elucidate the adhesion mechanism using ESCA, ATR-FTIR, contact angle measurements and iodometry. Among the species formed during the ozone treatment were several different carbonylic compounds, as well as hydroperoxides. The polar component of the surface energy increased for the ozone-treated materials as a result of the oxidation. Extraction of LDPE laminated with a regenerated cellulose film showed that strong bonding is achieved between the ozone-treated LDPE and cellulose during the lamination procedure. The suggestion proposed here for the adhesion mechanism is based on interactions between oxygen-containing species in both materials and the formation of covalent bonds originating from the decomposition of hydroperoxides.