Seventeen samples of the interspecific hybrid of thyme, Thymus × oblongifolius Opiz, were collected from thirteen different habitats in Lithuania. The composition of their essential oils was analyzed by capillary gas chromatography (GC) and mass spectrometry (MS). Eight chemotypes were defined, namely 1-octen-3-ol, (Z)-β-ocimene, geraniol, myrcene, 1,8-cineole, α-terpinyl acetate, germacrene B and geraniol/germacreneB. The composition of the hybrid oil can be characterized as intermediate comparing to its parental species, T. serpyllum L. and T. pulegioides L., according to the percentages of thymol, carvacrol, 1,8-cineole, germacrene B, geraniol and (Z)-β-ocimene. Three samples of the investigated T. × oblongifolius were moved from natural habitats into the experimental field collection and cloned annually in the ground under the same environmental conditions. Oil composition of these three samples was monitored in the fourth clonal offspring generation and compared with the oil composition of their parent plants from natural habitats. The results obtained by cloning showed that the composition of essential oil of the interspecific hybrid T. × oblongifolius is quite stable, most likely predetermined genetically.