XPS valence band spectra of 10 polymers (PE, PcI, PPG, PVME, PVA, PVMK, PAA, PMA, PMMA, and PGMA) were measured and simulated with the DMol ab initio molecular orbital program. We performed the calculations with model compounds such as trimers, pentamers, or hexamers of the polymers. The theoretical spectra of the oligomers show a good accordance with the experimental data. With the analysis of the calculated partial densities of states it is possible to assign the spectral features to specific atomic groups of the polymers. This gives a new detailed insight into the XPS valence band structure of the investigated polymers. The presented method could also be useful to obtain informations about the chemical structure of polymers with an unknown structure from the XPS valence band spectra.