Essential oils compositions of hydrodistilled fresh aerial parts of Thymus ciliatus (Lamiaceae), growing in various soils of Algeria and Morocco with different climates, are compared here. Carvacrol (0.2-80.3%), p-cymene (0.8-19.6%), γ-terpinene (0.2-14.6%), thymol (0.2-79.1%), camphor (7.5%), α-pinene (8.7%), α-terpinene (12.3%), trans-β-ocimene (25.8%) and nerolidol (6.9%) were the main components of the studied essential oils.