The electronic structure Of Cu2O is important for its application as a p-type transparent conducting oxide (TCO). To be useful as a TCO, a material needs to show enhanced transparency in the visible range (band gap >3 eV) as well as good conduction properties. While Cu2O has too small a band gap, alloys Of Cu2O and Al2O3 or Cu2O and alkaline earth oxides are known to display enhanced transparency, with little degradation of electrical properties. It is of interest to consider how to dope Cu2O p-type, e.g. Cu vacancies (oxidation) or cationic dopants. We present a study of the electronic structure and effective hole masses of stoichiometric and oxidised Cu2O and study metal cation doping, using density functional theory (DFT), to analyse p-type doping scenarios. We show that formation of a Cu vacancy is relatively facile, introducing delocalised hole states, with a light hole present. Substitutional cation doping with Al and Au/Ag is found to decrease the band gap but maintains a light hole effective mass necessary for p-type conduction. (C) 2007 Elsevier B.V. All rights reserved.