Deep levels in single crystals of CdSe intentionally doped with copper have been investigated by photoconductivity and space‐charge region capacitance techniques. The only center which can be conclusively associated with the copper impurity was found to have an activation energy of ∼1 eV with respect to the valence band. Estimates of 10−13and 10−18cm2were made for the hole and electron capture cross sections for this center. The capture cross‐section ratio of ∼105indicates that this center is behaving as a photoconductivity sensitizing center. However, another center with an activation energy of ∼0.65 eV with respect to the valence band, and which is commonly observed in undoped material, would appear to be the dominant sensitizing center for all but the highest levels of copper doping. Two further centers, with activation energies of ∼0.5 and ∼0.9 eV, relative to the conduction band, were also found. In addition, there is evidence for the existence of at least two distinct centers with the same activation energy of ∼0.2 eV with respect to the valence band, one of which appears to be copper related.