Abstract The chemical composition of the essential oils from the roots of plants identified as Thapsia maxima morphological types I and II and T. villosa diploid types 1 and 2, tetraploid types 3 and 4 and hexaploid type 5 has been investigated by GC and GC/MS. The oils from the different specimens of Thapsia were characterized by a high proportion of sesquiterpenoid components. The results are compared with those previously obtained from the fruits of the same plants.