| Summary: | The members of the <i>Inula candida</i> / <i>I. verbascifolia</i> group are perennial and chasmophytic plants attributed to four species and eleven entities at subspecific or varietal level. They are mostly confined to Greece. Volatile compounds of above-ground flowering parts of twenty-three populations covering ten taxonomic entities were obtained after hydrodistillation and analyzed by gas chromatography and mass spectrometry (GC-MS). In most cases, the total percentage of identified constituents reached 89% or above. Seventy-two components were identified. Oxygenated sesquiterpenes prevailed in the <i>I. candida</i> subgroup (47.3–71.5%), with <i>epi</i>-α-cadinol present in all members (13.4–42.7%) but rarely found in the <i>I</i>. <i>verbascifolia</i> subgroup. Considerable amounts of the hydrocarbon aldehydes decanal, undecanal and particularly tridecanal (0.5–35.0%, rarely absent) were predominately found in the <i>I. verbascifolia</i> members but were mostly absent in the <i>I. candida</i> subgroup. Isoalantolactone (12.4–49.5%), identified only in <i>I. subfloccosa</i>, and γ-(<i>Z</i>)-curcumen-12-ol, found only in <i>I. candida</i> subsp. <i>limonella</i> (22.6–42.1%), may serve as chemotaxonomic markers. Two different chemotypes can be distinguished within <i>I. verbascifolia</i> subsp. <i>aschersoniana</i>: a <i>trans</i>-muurola-4(14),5-diene-, γ-cadinene-rich chemotype from north-eastern Greece and a 1-<i>epi</i>-cubenol-, tridecanal-rich chemotype from central Greece. Different statistical algorithms were used to interpret the chemical diversity and identify the most appropriate number of clusters for the taxa. Cluster analyses indicated that the optimum number of clusters that best explain the metabolomic variability of the taxa is two. The degree of membership for each population based on the fuzzy k-means algorithm supported the <i>I. verbascifolia</i> subsp. <i>aschersoniana</i> samples within the <i>I. candida</i> subgroup, whereas <i>I. subfloccosa</i> may belong to any of the two clusters formed, although it also appears to have some unique characteristics.
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