Two nanosilica A-300/zirconia (SZ) composites at zirconia content CZrO2=5 and 20 wt.% were synthesized using a wet impregnation method with zirconium acetylacetonate as a precursor. The specific surface area of SZ is larger than that of A-300 because zirconia is composed of nanoparticles (crystallites of 4 nm in average size at CZrO2=20 wt.%) smaller than those of the initial silica (dav ≈ 11 nm). A-300 and SZ modified by polydimethylsiloxane (PDMS at molecular weight 1700 and 7960) in amounts of 5, 10, 15, 20 and 40 wt.% remained in the powder state with aggregates of primary particles smaller than those of A-300. SZ is more hydrophilic than silica but PDMS/SZ is more hydrophobic (maximum hydrophobic at CPDMS 15–20 or 40 wt.%) than PDMS/A-300.Graphical abstractHydrophobicity of PDMS/nanooxide nonlinearly depends on PDMS content and grafted zirconia.Highlights► Zirconia in the form of nanocrystallites grafted onto nanosilica increases specific surface area. ► Zirconia/nanosilica is more hydrophilic than nanosilica. ► PDMS/zirconia/nanosilica is more hydrophobic than PDMS/nanosilica. ► Hydrophobicity of PDMS/nanooxide depends nonlinearly on PDMS content.