The bonding between copper and oxygen atoms and its evolution with size has motivated extensive photoelectron spectroscopy measurements (see H. Wu, S. Desai, L.-S. Wang, J. Phys. Chem. A, 101 (1997) 2103-2777). Despite the small sizes involved in the experimental work carried out so far, the structure of the isomers is far from being elucidated. To go beyond qualitative interpretations, we have performed structural optimizations by using the first-principles molecular dynamics framework. The calculations on copper oxide clusters presented here are carried out within density functional theory (DFT), with a plane-wave basis set and generalized gradient corrections. Our results show that except in one case the CuO3 4 also exhibits planar geometry. Results obtained for CuO6 show that the symmetries deduced from the experiments do not correspond to the most stable forms, and are even unstable in some cases. More generally, the three largest clusters in the series are made of the structural blocks corresponding to the shape of the smaller isomers. Ozonides are favoured as the number of atoms increases. (C) 2003 Elsevier B.V. All rights reserved.