We present Molecular Dynamics simulation results concerning the structural properties of Cu and Au 2D adlayers on the Cu3Au(I 10) surface. We found that at low coverage the Cu adatoms occupy mainly dumbbell positions forming "pairs" with the Cu surface atoms, giving an incommensurate I x 4 aspect in the surface layer. It appears that this "pairing" stabilizes the surface preventing the location of Cu surface atoms at anti-sites. At higher coverage the Cu atoms reside at the four-fold adatom positions forming a well-ordered new type of "contracted" 2 x I Cu adlayer. Au deposition is characterized by wetting phenomena that take place very quickly already at low coverage and temperatures. An segregation occurs via exchange diffusion with the Cu surface atoms, resulting in mixed and disordered surface and adlayer. It comes out that these phenomena persist even close to the order-disorder bulk transition temperature. (C) 2003 Elsevier Science B.V. All rights reserved.