The chemical composition of the essential oils obtained by hydrodistillation of roots, stems with leaves and inflorescences of Valeriana italica Lam. and Valeriana tuberosa L. were studied by GC/MS. Seventy-three and forty-one constituents were identified from each plant, respectively. The major constituent of the oil obtained from the roots of V. italica was isolated and identified as 15-acetoxyvaleranone. Its stereochemistry and conformation has been studied using NMR spectroscopy and molecular modelling. The oils obtained from V. tuberosa completely lacked the characteristic valerane or kessane sesquiterpenes.