Polymer modified electrodes form a new field that combines polymer chemistry with electrochemistry and which aims at developing new materials for electrocatalysis, electronics, photoelectrochemistry and photoelectronics. This review describes the methods used to prepare polymer coatings on a carrier electrode and discusses various ways of controlling electron processes. The subjects treated include electron transport through the polymer layer, catalysis at the interface, charge storage for polymer batteries, display devices and polymer-based electronics. A central topic is electron pumping in the polymer layer by photophysical and photochemical processes activated by visible light. Several prospective applications are mentioned.