In the study, the antioxidant properties were investigated of commercial preparations of whey proteins that varied in the contents of protein and lactose. Antioxidant activity of those preparations was determined towards the ABTS^•+ radical cations and the peroxides in the linoleic acid emulsion. The determinations performed to characterize the proteins contained in the commercial preparations of whey proteins proved that the WPI 95 preparation was characterized by both the highest aromatic surface hydrophobicity and the highest contents of available groups of thiol and of lysine. All the preparations exhibited a high antiradical activity towards ABTS^•+. The WPC 60 and WPC 80 preparations showed the most effective deactivation of the ABTS^•+ radicals (approx. 76 %), whereas the lowest – the WPI 95 preparation (approx. 65 %). Among the preparations investigated, the highest antioxidant activity towards the linoleic acid emulsion was found in the case of WPC 34 and WPC 60, in which, except for proteins, the lactose was present in high amounts. This may suggest the interaction of those components and their increased impact on antioxidant activity.