Abstract Aiming to find out if any distinction between the Greek (Origanum vulgare ssp. hirtum) and Turkish oregano (O. onites) essential oils exists, the composition of six wild Greek populations of the former and four of the latter taxon were analyzed by means of GC and GC/MS. A PCA analysis showed that Turkish oregano oils had higher amounts of sabinene, myrcene, Î³-terpinene, borneol and carvacrol, and Greek oregano oils had higher p-cymene content. The latter were further divided into two subgroups, distinguished respectively by their thymol and carvacrol content. A comparison of our results with the published information showed that p-cymene percentages>14% and/or thymol>6% is found only in Greek oregano, while borneol content>2% is found only in Turkish oregano oils. Key Word Index: Origanum vulgare ssp. hirtum Origanum onites LamiaceaeGreek oreganoTurkish oreganoessential oil compositionp-cymeneborneolthymolcarvacrol