The coupling of liquid chromatography with FTIR spectroscopy opens up new and interesting ways to the detailed analysis of complex polymer systems. The application of this hyphenated technique to the analysis of polymer blends shows that it is possible to identify the different blend components by their spectral characteristics. Components of different chemical compositions are determined selectively and their chemical structure is analyzed through well resolved FTIR spectra. For structure elucidation, all facilities of state-of-the-art FTIR spectroscopy can be used. From the chromatographic and spectroscopic data contour diagrams are generated that present the molecular heterogeneity of the sample in the coordinates molar mass and chemical composition.