The paper discusses preparation and characteristics of silica hydrophobic layers deposited on the plasma-modified glass supports. The surfaces were investigated using wettability measurements, profilometry, photoacoustic and infrared spectroscopy, X-ray photoelectron spectroscopy as well as scanning electron microscopy. The wettability measurements showed that the obtained surfaces are hydrophobic – the water contact angle was in the range of 140-150 degrees. The photoacoustic and infrared spectroscopy as well as X-ray photoelectron spectroscopy disclosed the surface compositions, particularly that of the hydrophobic alkyl groups deposited on them. They were methyl groups introduced during hydrophobization by hexamethyldisilazane. In addition, it was found that the number of groups on the surface depends on the kind of plasma by which the supports were activated. The optical profilometer showed differences in the surface roughness which affects their hydrophobicity. Moreover, the surface free energies were determined using the contact angle hysteresis method. They disclosed differences in each surface, depending on the way of supports activation. The largest hydrophobicity was obtained on the layer deposited on the support activated by the argon plasma. However, support activation by the air plasma resulted in a decrease of hydrophobicity compared to that of the non-activated surface.