In this Letter, the interface geometry of silver thin films of thickness T between 1 and 3 ML epitaxially deposited at the MgO surface has been accurately characterized employing DFT periodic calculations. The Ag-Ag out-of-plane interlayer spacing is considerably shorter than the bulk values because of: (i) the reduced dimension; (ii) the perfect epitaxy constraint; (iii) the interaction with the substrate. The interface distance between the silver monolayer and the MgO substrate, d(Ag-O) = 2.60 Angstrom, is considerably longer than the estimates computed for the bilayer and the trilayer, d(Ag-O) = 2.47 and 2.48 Angstrom, respectively. The difference between the values of the interface distance computed for the monolayer and the results obtained for thicker films, lies in the peculiar electronic properties of the silver monolayer. (C) 2004 Elsevier B.V. All rights reserved.