Abstract Water distilled essential oils from two Umbelliferae species, which are endemic to Iran, were analyzed by GC/MS. α-Pinene (39.6%), β-pinene (23.9%) and β-phellandrene (9.5%) were the main components among the 33 constituents characterized in the oil of Peucedanum scoparium, representing 99.3% of the total components detected. Nineteen compounds were identified in the oil of Serotinocarpum insignis, representing 93.3% of the total oil with limonene (36.9%), β-pinene (17.4%) and myrcene (15.8%) as the major constituents. Both oils were richer in monoterpene than sesquiterpene hydrocarbons. Key Word Index: Peucedanum scoparium Serotinocarpum insignis Umbelliferaeessential oil compositionα-pineneβ-pinenelimonenemyrcene