The extraction of Hypericum perforatum L. by liquid carbon dioxide (p = 80 bar, t = 15 degreesC) gave almost the same extract yield (1%, w/w) as by supercritical (p = 100 bar, t = 40degreesC) carbon dioxide, containing the same percentages of essential oil (about 6.4%, w/w). The increase of the extract yield at higher pressure (250 to 350 bar) is due to the increase of extragent density, i.e., solubility. By increasing the grinding degree of the drug, a higher extract yield is obtained in the supercritical range under high pressure. GC-MS analysis of the extract composition showed that the non-terpene compounds have the highest contribution. The oil content in the drug, determined by steam distillation, was 0.058%, w/w. The oil content in the extracts, calculated for the drug, was significantly higher (1.2 to 1.9 times).