Free radical reactions have excited excessive research in the past two decades. Since then it has been proven that these mechanisms may be important in the pathogenesis of certain diseases and aging. Many synthetic antioxidant components have shown toxic and/or mutagenic effects, which have directed most of the attention on the naturally occurring antioxidants. Their use has mainly centered around prevention, and the maintenance of health. Parsley, Petroselinum crispum (Mill.) Nym. ex A. W. Hill belonging to the Apiaceae family, is a well-known spice and vegetable. Its herb and root are widely known for their effects on digestion, stomach, kidney, blood, and liver. The essential oil obtained from the fruit has also strong action on the central nervous system. Characteristic constituents are: flavonoids (apiin, luteolin-, apigenin-glycosides), essential oil (apiol, miriszticin), cumarines, (bergapten, imperatorin) and vitamin C. In our experimental work, various extracts prepared from different vegetative organs of parsley have been investigated. The chemical composition of the extracts and fractions were analyzed by chromatographic (GC, HPLC) and spectroscopic (UV, UV-VIS) techniques. We intended to provide evidence for the antioxidant activity of vegetable drugs and also studied the free radical scavenger activities by means of spectrophotometry (H-donor activity, reducing capability, chelat formation) and chemiluminometry. To prove the free radical scavenging effect of the extracts, the reduced intensity of the H2O2/.OH-isoluminol, microperoxidase system was studied in vitro. The highest correlation was found between the chemical property and the antioxidant effect of the flavonoid rich samples. At the same time it was also observed that the essential oil plays a significant role in the scavenging effect as well. More experiments are in progress to study the most promising compounds in the vegetative and generative organs of parsley.