This paper proposes a three-dimensional system for modelling stress in thin films deposited on thick substrates deformed as a small cylindrical surface by means of the minimization of the deformation energy. The results show the validity limits of the well-established Stoney equation and indicate the necessity of a correction term for substrates with Poisson ratio (nu(s)) in the range of 0.25 < nu(s) < 0.4. (C) 2010 Elsevier B.V. All rights reserved.