Spectroscopic ellipsometry (SE) and quartz crystal microbalance with dissipation (QCM-D) techniques have been extensively used as independent surface characterization tools to monitor in-situ thin film formation. They provide different information for ultra-thin films because QCM-D is sensitive to the solvent content while SE is not. For using these two techniques in tandem, we present a virtual separation approach to enable the determination of both ultra-thin film thickness and porosity. Assumptions for the intrinsic molecular polarizability (index of refraction n(o)) and density (rho(o)) of the organic adsorbent must be made, and the consequences for these parameters' values are discussed. (C) 2010 Elsevier B.V. All rights reserved.