Xylella fastidiosa Wells et al. (Xanthomonadales: Xanthomonadaceae) is a xylem inhabiting bacterium which is exclusively transmitted by xylem sap feeding insects. Among them, Philaenus spumarius Linnaeus and Neophilaenus campestris Fallén are the most abundant species in Europe. During 2018 and 2019 a survey was conducted in olive groves in Greece aimed to improve the knowledge about the biology and ecology of those spittlebugs in areas with Mediterranean climate. Moreover, the host preference of the nymphs was studied. The nymphs of P. spumarius and N. campestris were observed between early March and middle May depending on geographic location and year. The spittlebug adults were present during two periods every year, one in spring and another one in autumn and early winter. During summer months the spittlebugs were totally absent from olive groves. Our observation on host plant selection revealed that there was a strong preference of N. campestris nymphs for plants belonging to the family Poaceae. On the contrary, P. spumarius nymphs were polyphagous. The most preferable plants for the nymphs of this species belonged to the families Asteraceae and Fabaceae. The importance of these findings for control measures for these spittlebugs is discussed.