The essential oils from Cantinoa carpinifolia (Benth.) and Lippia origanoides (Kunth.) were obtained by hydrodistillation. The constituents were determined by GC-MS and GC-FID. The antioxidant activities were evaluated by the ABTS, DPPH and hydroxyl radicals, phosphomolybdenum complex, reducing power, β-carotene/linoleic acid and the TBARS methods. Analysis of variance and the ScottâKnott test of the means at 5% were performed. The principal constituents in the essential oil from C.carpinifolia were α-thujone (32.15%) and β-thujone (22.22%), whereas carvacrol (41.51%), p-cymene (18.36%) and γ-terpinene (17.03%) were obtained from L.origanoides. The respective IC50 for the essential oils from C. carpinifolia and L.origanoides in the ABTS tests were >1000 and 110 µg mLâ1; DPPH (110 and >1000 µg mLâ1), hydroxyl (636 and 484 µg mLâ1), β-carotene (>2000 and 215 µg mLâ1) and TBARS (778 and 527µg mLâ1). The L. origanoides essential oil was the most effective antioxidant.