Introduction. Many underutilized wild fruits have great nutritional andfunctional potential, providing chemical compounds with biological properties.Materials and methods. In the present work we quantified bioactivecompounds such as vitamin C (ascorbic and dehydroascorbic acids), and total phenoliccompounds composed mainly of phenolic acids, flavonols and anthocyanins, as well asevaluating the antioxidant capacity through different in vitro tests(Folin-Ciocalteu, ABTS·+, DPPH· and FRAP) in wild blackthorn (P. spinosaL.) and hawthorn (C. monogyna Jacq.) fruits of Spanish origin, includingsamples from different seasons and locations. Results and discussion. Asexpected, wide variability was found in the composition of fruits of the same species,which justifies the necessity of analyzing several batches of wild fruits, in order tohave representative results taking into account the natural variability. Fruits ofP. spinosa showed vitamin C content ranging between (5.14 and15.35) mg·100 g–1 fw (mainly dehydroascorbic acid); total phenolic compounds ranged from(1851 to 3825) mg·100 g–1 fw, characterized by a high content of anthocyanins and phenolicacids. Fruits of C. monogyna presented (16 to 39) mg vitamin C·100 g–1 fwand (449 to 1438) mg total phenolic compounds·100 g–1 fw, characterized by a high contentof phenolic acids and flavonols. Antioxidant capacity was higher forP. spinosa fruits than for C. monogyna fruits; DPPH·values showed a strong correlation with vitamin C, while phenolic compounds were a majorcontributor to the antioxidant activity of these fruit extracts. Fruits ofP. spinosa and C. monogyna should be reconsidered asnew valuable sources of safe and inexpensive antioxidants.