Ocimum basilicum (sweet basil) is an important essential oil plant used for different purposes (from food flavoring to pharmaceutical applications) characterized by the presence of several chemotypes. Here we show a comparative analysis between hydrodistillation of essential oils (EO) and supercritical CO2 extraction (SFE) of an O. basilicum chemotype particularly rich in T-cadinol. SFE yielded a higher percentage of 1,8-cineole (10%; 4-fold), linalool (23.2%; 5.8-fold), eugenol (13.3%; 1.2-fold) and germacrene D (5.6%; 28-fold) with respect to EO. On the other hand, EO composition was characterized by higher percentages of T-cadinol (27.5%; 3-fold) and some other sesquiterpenes with respect to SFE. The presence of high percentages of T-cadinol in EO is of great importance owing to the biological activity of this compound in cancer therapy and as an antibiotic.