The content and composition of the polyphenolic compounds and the activity of polyphenoloxidase were determined in some plum varieties popular in Poland: węgierka Dąbrowicka, Zwykła, Łowicka, Stanley, and also in wild plum - ałycza. The total polyphenols content in investigated plums, as well as anthocyanins and flavanols, was rather low (160-300mg/100g, 18-33 mg/100 g and 9-14 mg/100 g of fruits, respectively). (+)Catechin occurring in quantities from 1.3 to 3.9 mg/100 g was found to be a dominant compound representing biologically active monomers and dimers of flavanols. The highest quantities of hydroxycinnamic acids, especially neochlorogenic one, (46 - 85 mg/100 g) are found in all plum varieties. The main anthocyanin pigments of plums are cyanidin-3-glucoside and cyanidine-3-rutinoside; they make up 42 to 62% of the total anthocyanins. All investigated plum varieties show high polyphenoloxidase activity but there are substantial differences between particular varieties ranging from 3200 to 17200 U/g.