Background: Thymus deanensis is a known aromatic plant which grows widely in Iran and many mediterranean regions. In previous studies composition of essential oils of many species of Thymus genus reported which they were rich of phenols like Thymol and Carvacrol. Methods: Water distilled essential oils from aerial parts of Thymus deanensis var. deanensis from three different localities in Iran were analyzed by GC and GC/MS. Results: 20 compounds representing 87.8% of the region of Azerbaijan Mountains (A) oil were identified with thymol (70.8%), carvacrol (6.3%) as main constituents. 13 compounds representing 98.6 % of Damavand, Mosha (B) oil were identified with thymol (53.6%), carvacrol (23.8%) and p-cymene (11.0 %) and then thymol (72.1%) and p-cymene (5.3%) were the major constituents of the latter oil Chaharmahal Bakhtiari (C) among the 16 compounds characterized which represented 99.6% of the oil. Conclusions: The composition of three samples of Th. deanensis oils in our research was similar to the composition of other phenol–rich Iranian species. Although the content of thymol in Th. deanensis is higher than many reported cultivated Thymus vulgaris.