Sorption is an underlying process in determining the fate and transport of hydrophobic organic contaminants (HOCs) in soils and sediments. Also, it is known that soil/sediment organic matter (SOM) is the predominant sorbent for HOCs. In 1990s, aromatic structures of SOM were reported to be primarily responsible for HOCs sorption, supported by positive correlations between aromaticity and organic carbon normalized sorption coefficients (Koc). Recently, aliphatic components, particularly paraffinic carbons, of SOM are reported to sorb significant amounts of HOCs, similarly supported by positive correlations between aliphaticity and Koc values. From a series of sorption experiments, and spectroscopic and elemental analyses, we concluded that both aromatic and aliphatic components can be important for HOCs sorption, but polarity of SOM seems to be a determining factor for the magnitude of Koc, which is line with the observation in the literature and by us that Koc values are inversely proportional to the polarity of SOM as expressed by atomic ratio [(O+N)/C] or by polar carbon contents obtained from NMR spectra. In addition, sorbents with high Koc are often associated with low polarity whether their structures are highly aromatic or aliphatic.