Abstract The essential oil of three populations of Calamintha sylvatica Bromf. native to the mountain region of southwestern Serbia and one population of Calamintha vardarensis Å ilic from southern former Yugoslav Republic of Macedonia were studied. The highest oil yields were found in C. vardarensis (1.54%), whereas in C. sylvatica oil yields varied from 0.11% up to 0.94%. In all samples, cis-piperitone oxide was a major compound. The highest percentage was found in the oil of C. vardarensis (65.6%). In C. sylvatica piperitone oxide varied from 48.9â59.2%. In the examined samples, oil composition appeared to vary more according to geographical rather than genetic factors.