This work aims to detail the mass change of a porous silicon sample during copper immersion plating. Gravimetric measurements and quantification of the deposited copper by induced coupled plasma spectroscopy (ICP) permit to separate the contributions to the mass change. The results indicate that immersion plating proceeds independently of the porous layer thickness at short immersion time. However, after long immersion duration, the deposition stops and thick porous layers are not fully oxidised. The oxidation of the porous layer is homogeneous and proceeds in depth with time, down to several micrometers. (C) 2004 Elsevier Ltd. All rights reserved.