The present invention is directed to methods for improving the performance of an electrophoretic display by modifying the display cell surface. More specifically, the methods are directed to modification of the microcup surface after the microcups are released from the mold. The microcups which have undergone any of the treatment methods of the invention show significant improvement in their surface properties, such as chemical functionality, surface roughness, surface tension, morphology, surface charge, surface reflectivity, surface conductivity and optical properties, particularly optical density in the visible light region. An electrophoretic display formed from the treated microcups has many advantages. For example, the display shows a higher contrast ratio, lower electro-optic response time, lower driving voltage, longer shelf life, higher imageincreasing bistability and higher threshold voltage. In addition, it exhibits an improved image quality by reducing undesirable scum formation or irreversible particle deposition on the microcup surface.