Chromium oxyselenide Cr2Se0.71O2.30 was synthesised by chemical vapor synthesis of chromium oxychloride and diethyl selenide. The material adopts the Cr2Se3 structure type with a = 6.26(3) Å and c = 17.45(3) Å. The Raman spectrum shows bands at 225 and 550 cm–1. X-ray photoelectron spectroscopy and wavelength dispersive analysis by X-rays confirmed the material was homogeneous and of uniform composition Cr2Se0.71O2.30. The material is an antiferromagnet with a Neel temperature of 43 K. This is the first solid-state chromium oxyselenide reported and shows that the hard oxygen and soft selenium can co-exist in the same lattice if formed under the kinetic product conditions of a rapid gas-phase reaction.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)