For the female pistachio (Pistacia vera L.) cultivars 'Bianca', 'Kerman', 'Larnaka' and 'Red Aleppo' and the male cultivars 'Ask' and 'Peter', the following parameters were assessed by means of a portable infrared gas analyser: net carbon dioxide assimilation, stomatal conductance, transpiration, photosynthetic photon flux, photosynthetic efficiency and water use efficiency. The two male genotypes, characterized by high stomatal conductance and transpiration rate and by high to medium net CO2 uptake, were separated from the other cultivars by principal component analysis. As for female cultivars, 'Larnaka' and 'Bianca' showed the highest and the lowest rate of carbon assimilation, respectively, 'Kerman' and 'Red Aleppo' were very close to each other. Moreover, 'Larnaka' achieved the best compromise between assimilation and transpiration rates, as indicated by its higher water use efficiency.