Abstract The essential oil composition of two endemic species of Centaurea, C. paniculata subsp. carueliana and C. rupestris (Asteraceae) collected on serpentine rocks on Mt. Ferrato (Tuscany, Italy) were investigated by GC and GC/MS. Several classes of compounds were detected, of which sesquiterpenes, (representing the 25.6% of the total oil from C. paniculata and 74.5% from C. rupestris), alcohols (27.8% in C. paniculata and 4.3% in C. rupestris) and aldehydes (12.0% C. paniculata and 2.0% in C. rupestris) were the most abundant, followed by acids, monoterpenes, esters, ketones, hydrocarbons, diterpenes and miscellaneous. A series of unidentifed compounds were also detected. Differences in qualitative and quantitative composition were evidenced and discussed.