The structure of vapour-deposited CdSe films was found to be random. However, on annealing, grain growth occurred with the basal plane parallel to the plane of the film. The crystal structure indexed to the hexagonal Wurtzite form but substrate defects resulted in non-uniformity of the film and the CdSe in these regions contained a strong component of grains oriented with the basal planes perpendicular to the films. In addition the larger grains produced by grain growth contained a high density of planar faults probably as a result of stacking disorder. The chromium contact pad used in thin film transistor devices is not stable. During the annealing process chromium diffuses laterally into the CdSe producing circumferential regions of different grain size. Also there is a reaction between chromium and CdSe resulting in the formation of columnar grains of chromium-deficient chromium selenide and the release of elemental cadmium. © 1980.