The photostability of bisphenol-A polycarbonate (PC) can be increased by depositing zinc oxide (ZnO) coatings onto PC films by radiofrequency (rf) magnetron sputtering using an Ar-O-2 plasma. The photoprotective efficiency increases with the thickness of the ZnO layer and also depends on the sputtering parameters (rf power, total pressure, plasma composition), which control the properties of coatings. The increasing thickness of the deposits is correlated with variations of the density, grain size, and composition. PC samples with ZnO coatings were submitted to artificial accelerated ageing (lambda > 300 nm) and the extent of the photodegradation was evaluated by infrared and UV-visible spectroscopies. All the deposition parameters were optimized as a function of the results obtained in photoageing and are described in this article. (C) 2004 Wiley Periodicals, Inc.