Adsorption of water molecules on the CdZnTe (1 1 1) B surface has been studied at room temperature using synchrotron radiation ultraviolet photoemission spectroscopy (SRUPS), X-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED). After water exposure, the Cd 3d core level is chemically shifted by -0.5 eV, and in the valence band, three water-induced orbital levels are found at -3.6, -4.8 and around -8.5 eV below the Fermi level. They can be assigned to water molecules adsorbed on Cd atoms. Together with the observed work function decrease, we suggested that water is adsorbed oxygen-end-down. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.