Extra virgin olive oil (EVOO) is one of the most important vegetable oils from an economic and nutritional point of view. The health properties and oxidative stability of this oil depend on its chemical composition. However, these attributes are affected by the type of cultivar and the climate in which the olive trees are grown. This study was carried out to determine the fatty acid composition (FA) and the amount of polyphenols (PT) including hydroxytyrosol (HT) in 4 EVOO obtained from ‘Coratina’, ‘Arbequina’, ‘Barnea’ and oil blend (‘Barnea’ and ‘Arbequina’) varietals grown in a semi-arid region of northwestern Argentina. The ‘Coratina’ variety had a high oleic acid content (72.875%), and a higher monounsaturated and polyunsaturated fatty acids (MUFA/PUFA) ratio. PT values were significantly higher for the blend (280 mg/kg) than for ‘Arbequina’ (268 mg kg-1), ‘Barnea’ (248 mg kg-1) and ‘Coratina’ (210 mg kg-1). The HT content ranged from 3 mg kg-1 oil (‘Arbequina’) to 0.6 mg kg-1 oil (Blend). It is evident that all the oils analyzed contain nutritionally important elements which are determined by the varietal component of each one of them, and to a lesser extent by the soil and climatic conditions of the production region. These data could be useful to facilitate the selection of olive varieties planted in this semi-arid region, capable of producing EVOO with distinctive signs and better food quality.