Sour cherries are rich in bioactive compounds. The present study aims to research the stability of ascorbic acid and the dynamics of total phenolic and flavonoid contents, as well as some enzymatic activities (ascorbate oxidase, superoxide dismutase, catalase, polyphenol oxidase and peroxidase) during different operations of the technological process of jam fabrication. Their evolution during jam storage was also studied. Ascorbic acid was comparatively analyzed using 3 different methods (HPLC, Reflectoquant and 2, 6-dichlorophenolindophenol method). The jam manufacturing processes determine strong ascorbic acid degradation, which emphasizes during storage, especially at room temperature (25 °C). But, total phenolic content is very high in the finished product, registering only a slight decrease compared to the raw material. The enzymes are inactivated during the jam fabrication.