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The composition of leaf and flower essential oils of eight Heracleum taxa (populations collected in Serbia, Montenegro, North Macedonia and Slovenia) was statistically analyzed to evaluate its chemosystematic significance. Investigated taxa included H. orphanidis and the representatives of H. sphondylium group: H. sphondylium, H. sibiricum, H. montanum, H. ternatum, H. pyrenaicum subsp. pollinianum, H. pyrenaicum subsp. orsinii and H. verticillatum. Hydrodistilled essential oils were analyzed by GC–FID and GC–MS. Chemosystematic significance was evaluated using multivariate statistics: principal component analysis (PCA), non-metric multidimensional scaling (NMDS) and unweighted pair-group arithmetic averages clustering (UPGMA). Statistical analyses included our previously published data on the composition of essential oils of eight leaf and three flower samples, as well as the data on the composition of the oils of additional eight leaf and five flower samples obtained in the current work. Leaf and flower essential oils of H. sphondylium group members were dominated by various sesquiterpenes, phenylpropanoids and/or monoterpenes. Heracleum orphanidis leaf and flower essential oils were rich in aliphatic esters, mostly octyl acetate. Statistical analysis of the composition of leaf essential oils, as well as of flower oils, demonstrated the grouping of investigated populations of these Heracleum taxa according to their systematics, i.e., separation of H. orphanidis from the representatives of H. sphondylium group, and grouping of H. pyrenaicum subspecies within this group. Morphologically related H. sibiricum and H. ternatum were closely located in PCA and NMDS and in UPGMA even shared the same cluster. [ABSTRACT FROM AUTHOR]