Thirteen Hypericum species growing in Bulgaria were investigated for free radical-scavenging activity, antioxidant activity, total tannins and total flavonoids contents. Methanolic extracts from the Hypericum species were analyzed for radical scavenging and antioxidant activities using DPPH-, ABTS- free radicals, total antioxidant activity and inhibition of lipid peroxidation by ferric thiocyanate (FTC) method. Butylated hydroxytoluene and ascorbic acid were used as positive controls. Methanolic extracts from H. cerastoides, H. perforatum and H. maculatum demonstrate the highest antioxidant activities and are potential sources of natural antioxidant compounds. The quantification of tannins and flavanoids were determined in Hypericum species using Folin-Chiocalteu reagent and AlCl3, respectively. The amounts of the tannins ranged from 1.30 ± 0.01 mg/100 g dw in H. elegans to 8.67 ± 0.02 g/100 g dw in H. perforatum. The highest concentration of flavonoids was found in H. cerastoides (1.22 ± 0.02 g/100g dw), and the lowest amount was established in H. olympicum (0.20 ± 0.03 g/100g dw).