Introduction: Quince (Cydonia oblonga Mill.) is a plant of which both the fruits and the leaves are sources of compounds with antioxidant potential. Such activity could be helpful to prevent the development of socalled oxidative stress. Objective: The aim of the study was to evaluate the antioxidant properties of ethanolic, methanolic and acetonic extracts of mature and immature quince fruits, as well as leaves. Methods: The extracts were prepared using ultrasound-assisted extraction, for 15, 30 and 60 minutes. The antioxidant activity was assessed by DPPH, FRAP, ABTS and Folin-Ciocalteu (F-C) methods. Results: Antioxidant activity of all of the evaluated extracts were observed. The highest potential determined with each method was found for leaf extracts. Moreover, higher activity of unripe fruit extracts compared to ripe fruit was observed. Taking into account the applied extractants, the highest antioxidant capacity was found for methanolic extracts, extracted for 60 and 30 minutes. By contrast, the lowest potential was observed mainly for ethanolic extracts (extraction time 15 minutes). Conclusion: Quince extracts, particularly alcoholic extracts of leaves, seem to be a valuable source of antioxidants. Factors as extraction time, the type of solvent and degree of fruit maturity may influence the antioxidant activity of extracts.