Physalis alkekengi L. (bladder cherry, Chinese lantern, winter cherry) is an unusual species of the family Solanaceae. Although accumulation of alkaloids is characteristic to Solanaceae species, and accordingly the root and above ground parts of P. alkekengi are toxic, its fruits are in exceptionally edible. The present paper deals with the investigation of antioxidant hydrophilic compounds of the fruits in order to find correlation between the quantity of the constituents and antioxidant capacity of the extracts. Dried and fresh, freeze stored fruits were extracted with water, and the ascorbic acid and total polyphenol content of the fruits was determined. Furthermore, the antioxidant effect was investigated by DPPH test, and in vitro using the rat-brain homogenate method. The antioxidant activity measured by DPPH (fresh fruit: IC50 = 2.48 mg/ml; dried fruit: IC50 = 22.32 mg/ml) showed good correlation with the ascorbic acid content of the fruit (fresh fruit: 1.095%; dried fruit: 0.162%), and exhibited substantial decrease due the drying process. Lipid peroxidation inhibitory activity was found to be weaker as the DPPH radical scavenger capacity, however, also showed a decrease during the drying process of the fruit (fresh fruit: IC50 = 6.43 mg/ml; dried fruit: IC50 = 15.59 mg/ml). Our results clearly demonstrated the radical scavenger and lipid peroxidation inhibitory activity of aqueous extracts of bladder cherry, and indicate that the conservation and processing technology significantly influenced the antioxidant activity and the content of the active ingredients.