| Summary: | The chemical composition of the volatile fraction from <i>Galium verum</i> L. (leaves and flowers) and <i>Cruciata laevipes</i> Opiz (whole plant), <i>Rubiaceae</i>, was investigated. Samples from these two plant species were collected at full bloom in Val di Susa (Western Alps, Turin, Italy), distilled in a Clevenger-type apparatus, and analyzed by GC/FID and GC/MS. A total of more than 70 compounds were identified, making up 92%–98% of the total oil. Chemical investigation of their essential oils indicated a quite different composition between <i>G. verum</i> and <i>C. laevipes, </i>both in terms of the major constituents and the dominant chemical classes of the specialized metabolites. The most abundant compounds identified in the essential oils from <i>G. verum</i> were 2-methylbenzaldheyde (26.27%, corresponding to 11.59 μg/g of fresh plant material) in the leaves and germacrene D (27.70%; 61.63 μg/g) in the flowers. <i>C. laevipes</i> essential oils were instead characterized by two sesquiterpenes, namely β-caryophyllene (19.90%; 15.68 μg/g) and <i>trans</i>-muurola-4(15),5-diene (7.60%; 5.99 μg/g); two phenylpropanoids, benzyl alcohol (8.30%; 6.71 μg/g), and phenylacetaldehyde (7.74%; 6.26 μg/g); and the green-leaf alcohol <i>cis</i>-3-hexen-1-ol (9.69%; 7.84 μg/g). The ecological significance of the presence of such compounds is discussed.
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