This paper is an attempt to understand how Polycaprolactone-b-Polymethyl Methacrylate diblocks (PCL-b-PMMA) are organized in a confined geometry such as nanometric thin films spin coated on gold coated substrates. Polarization-Modulation Infrared Reflection Absorption Spectroscopy (PM-IRRAS), employed to characterize PCL-b-PMMA thin films, allowed us to suggest an adsorption model of PCL-b-PMMA diblock copolymers in which PCL chains are almost perpendicular to the substrate plane, while PMMA blocks seem to be flattened at the surface. These results were also supported by Atomic Force Microscopy (AFM) that was extremely useful for the comprehension of PCL-b-PMMA diblocks behavior when adsorbed as thin films. The combination of the experimental observations offered us the possibility to propose a model of chain folding in the PCL-b-PMMA diblock copolymers after adsorption on chemically inert substrates. (c) 2005 Elsevier B.V. All rights reserved.