Juniperus communis or common juniper is the only conifer with pan-arctic distribution due to its polymorphic nature and high phenotypic plasticity. This taxon also produces large amounts of essential oil, which are stored in resin ducts in leaves (needles) and seed-cones. Leaf terpenoid composition of 97 individuals of common juniper from five populations in north-western Balkans was investigated. In total, 135 compounds were identified, representing on average 99.2% of the composition. Sabinene was the most abundant compound in most of the samples, followed by Î±-pinene and terpinen-4-ol. Two populations that were located deeper into the peninsula had a higher fraction of sesquiterpenes in comparison to the more coastal populations and one Julian Alps population. Multivariate statistical analyses also confirmed the separation of populations based on the essential oil composition. There was no correlation found between chemical composition and environmental factors. Chemophenetic implications are briefly discussed.