The paper gives an overview on the influence of point defects on electronic properties of interfaces including band alignment (barrier heights) and transport properties. As examples interfaces between metals and the II-VI semiconductors CdTe and ZnTe are presented. In addition untypical phenomena at semiconductor heterocontact formation at In2S3/ZnO and CuInSe2/CdS interfaces is described. It is suggested that the barrier heights as well as the transport properties at both interfaces are strongly affected by defects, which are either present because of non-stoichiometry of the materials or introduced by contact formation due to chemical interactions.