Two synchrotron set-ups have been used to carry out in situ strain measurements on systems constituted by Au films on polyimide substrates. These film/substrate composites have been submitted to either uniaxial or equibiaxial loadings. For the two configurations, an area detector (2D) was employed to extract the so-called epsilon-sin(2) psi curves. These latter are shown to be affected by geometrical effect unless equibiaxial loading is employed. Moreover, non-linearity of these curves can occur, even in the case of equibiaxial loading, when the film is thin (120 nm). This last phenomenon is explained by surface anisotropy. (C) 2012 Elsevier B. V. All rights reserved.