The chemical composition and the antioxidant activity of the volatile fraction of a naturalized population of parsley [Petroselinum crispum (Mill) Nyman] were assessed and compared in a field trial with those of three commercial cultivars. Volatile oils extracted from the leaves were analysed by GC/FID and GC/MS. A total of twenty compounds were detected in all accessions, being the most representatives the terpenes 1,3,8-p-mentathriene and Î²-phellandrene and the phenylpropanoid myristicin. The naturalized population differed from the cultivars for the highest yield of volatile oil, which was characterized by the absence of apiole, a lower content of myristicin and the highest amount of 1,3,8-p-mentathriene. The antioxidant activity of the essential oil from the evaluated accessions was very low. Due to its essential oil yield and composition, the naturalized population could be taken into consideration for the starting of a breeding programme.