As a worldwide challenge, the oil spillage has gained tremendous attention within the last few years. In this work, a facile method is proposed to fabricate sponges treated with polydimethylsiloxane (PDMS) and modified/unmodified silica nanoparticles exhibiting superhydrophobic and superoleophilic properties for enhanced oil/water separation. The main aim is to delineate the role of surface composition versus surface morphology by employing different formulations. Scanning electron microscopy results demonstrated that a rough structure, induced by formation of a packed assembly of nanoparticles, gives a major contribution to the obtained superhydrophobic behavior. It was also proved that the surface modification of silica nanoparticles might play an even more important role in attaining superhydrophobicity. Once a combination of PDMS and modified silica was used, different oil/ water mixtures were efficiently separated. On the other hand, surface composition of the coating was found to be the major factor affecting wettability of sponges and their capability to separate water/oil mixtures. Therefore, results of this study can be used as a hint for designing more efficient sponge-based systems modified with polymer nanocomposites for oil/water separation applications. POLYM. COMPOS., 00:000-000, 2018.