The effects of corona discharge treatment (CDT) on ink drop impact and spreading on a coated polypropylene film substrate were investigated. Substrate surface energies were determined from static contact angles with water and ethylene glycol. The polar component increased with increasing CDT. Drops 39 μm in diameter of an acrylate-based UV-curable ink were printed on to the substrate, and the spreading process studied by high-speed photography. No changes occurred during the initial stages, but the wetting phase was shorter for higher doses of CDT. Drops spread further on substrates with low doses of CDT than with higher doses. White light interferometry was used to determine the final heights of drops after UV-curing. The height was significantly affected by CDT, with minimum height at low doses. The relationship was investigated between the static contact angle for large sessile drops and the equilibrium contact angle for printed drops after spreading. Contact angle measurements with millimeter-sized sessile drops of ink provide a reliable method to determine the effects of corona treatment on wetting by ink jet printed drops.