The objective of this study was to compare the effect of probiotic fermentation (conducted by L. acidophilus LA-5) of milk containing an addition of selected whey or milk protein preparations (whey protein concentrates, whole milk, whey protein isolate, casein glycomacropeptide or a-lactalbumin) on the technological and functional properties of obtained milk beverages. Determination of the antioxidative activities and identification sequences of biologically active peptides generated in selected protein preparations during probiotic fermentation also constituted the aim of the research. The results obtained indicate that the addition (1%) of a-lactalbumin into regenerated skimmed milk in the highest degree reduced the syneresis level in fermented products. Also, a-lactalbumin hydrolysates exhibited the strongest antioxidative properties (57.57±6.6%), while casein glycomacropeptide hydrolysates allowed us to obtain the highest amount of various biopeptides.