In this mini review we present a short summary of our research work in the XPS spectroscopy study of the interface between π-conjugated polymer films and deposited metals. The investigated materials are organic and organometallic polymers that have been used in the preparation of gas-sensing devices or studied for their non linear optical properties. The here considered metals (Cu, Cr) were deposited step by step onto the polymer film surface. The core level signals evolution of the polymer substrate and of the metal overlayer was studied as a function of the metal thickness from the submonolayer region up to a thickness of several monolayers. The experimental results yielded information on the nature of the chemical interaction at the interface (chemical bonding, charge transfer processes, formation of new chemical species), on the active centers and on the metal growth mode on the polymer surface (layer-by-layer, cluster growth or mixed).