Cornelian cherry (Cornus mas L.), apple (Malus domestica Borkh. cultivars Jonagold and Red Boskoop), pear (Pyrus communis cv. Conference), and plum (Prunus domestica L. cv. Common Plum) juices were assayed for their quality, organic acids, polyphenol content, and antioxidant activity (determined as a ferric-reducing antioxidant power [FRAP]). Cornelian cherry juice revealed the highest titratable acidity-2.58 g malic acid/100 g. The highest polyphenol content was also noted for Cornelian cherry-45.6 mg gallic acid (GA)/g. The medium level of polyphenols was proved for Jonagold apple (22.8 mg GA1/g). The lowest level was recorded for Common Plum (9.60 mg GA/g), followed by Conference pear and Red Boskoop apple (12.3 and 21.3 mg GA/g, respectively). The FRAP values were 1.97 mmol Fe/L for Common Plum juice, 2.37 mmol Fe/L for Conference pear juice, and 3.92 mmol Fe/L for both Red Boskoop and Jonagold apple juices. However, the obtained data indicated outstanding antioxidant properties for Cornelian cherry juice. In this case, FRAP reached 23.5 mmol Fe/L. The calculated correlation coefficient FRAP versus polyphenols indicates that the antioxidant status for Cornelian cherry is not only correlated with polyphenols but also with other biological compounds. The obtained results indicated that Cornelian cherry is a valuable source of substances with a high antioxidant activity.