The objectives of this study were to investigate the effect of the enzymatic hydrolysis conditions on the properties of whey hydrolysates as protein patterns, degree of hydrolysis (DH) and reactive oxygen species (ROS) scavenging activity and to investigate the stability of whey hydrolysates. Enzymatic hydrolysis conditions of whey were performed at various types of enzyme (trypsin, chymotrypsin and papain), enzyme to substrate ratio (E/S: 1/1000, 1/200 and 1/100) and hydrolysis time (1, 3 and 5 hr). From the protein patterns of whey hydrolysates, increased E/S and hydrolysis time improved the digestion of whey by trypsin and chymotrypsin. While the digestion of whey by papain was increased by the E/S. Increased E/S and hydrolysis time resulted in increasing the DH of whey hydrolysates. Papain had the greatest digestive ability to hydrolyze whey followed by trypsin and chymotrypsin. The ROS scavenging activity of whey hydrolysates was investigated in human keratinocyte cells (HaCaT cells). The types of enzyme had the greatest effect on the activity. Whey hydrolyzed with papain showed the highest activity followed by whey hydrolyzed with trypsin and chymotrypsin. Although whey hydrolysates were rich in cysteine, a glutathione precursor, our study showed that the ROS scavenging activity of whey hydrolysates was not mediated by the stimulation of glutathione synthesis. The stability of lyophilized whey hydrolysate powders was investigated under accelerated condition. After 3 month’s storage, the peptides in whey hydrolysate powders were unstable resulting in decreased ROS scavenging activity.