Two polyurethane blends-poly(carbonate urethane)/poly(vinyl alcohol) [PCU/PVA] and the aliphatic poly(ether methane) (Tecoflex(TM))/poly(pentanedioic acid mono-4-(acryloyloxy)butyl ester) [Tecoflex(TM)/COOH]-were surface-modified. Poly(vinyl alcohol) [PVA] and poly(4-hydroxybutyl acrylate) [PHBA] were used as model surfaces. 4-Isocyanato butanoic acid methyl eater was coupled as a spacer molecule to PVA and the PVA-containing polyurethane blend. Saponification of the generated ester group was verified by means of Electron Spin Resonance (ESR) spectroscopy using the nitroxyl radical 4-amino-2,2,6,6tetramethylpiperidine-1-oxyl (4-amino-TEMPO) as a reporter group. In the case of Tecoflex(TM) and PHBA, glutaric anhydride served as a spacer molecule. 4-Amino-TEMPO was coupled to this spacer as well. ESR spectroscopy as a bulk method was used together with the surface-sensitive method X-Ray Photoelectron Spectroscopy (XPS) verifying the modification steps by elemental composition, ESR line shapes, and determination of the rotational correlation time tau(c).