Agroecosystems often dominate in Mediterranean area and their management strongly affects biodiversity. In Greece, about one third of the olive groves are organic – with environment friendly farming practices - while the rest includes conventional or abandoned olive groves. The current study aims to investigate plant species diversity of olive groves under different management practices. Authors unpublished data from field surveys on different insular and mainland areas have been used, together with already published data. The results showed that organic olive groves are characterized by a rich and diverse flora, mainly dominated by therophytes and especially of annual leguminous species and other insect-pollinated plants that are indicators of long-term but moderate human interference. Conventional olive groves have a poor and rather common flora also dominated by therophytes. Abandoned olive groves present a rather poor but diverse flora, mainly dominated by hemicryptophytes and phanerophytes and to a lower proportion of annual plants, depending also on when they have been abandoned.