This work presents a summary on water resource availability in Greece with an emphasis on irrigation water use since about 85 percent of water withdrawal is for agricultural purposes. Irrigation methods, crop water requirements, crop production and crop water productivity data are elaborated are discussed. The state of art of research and agricultural activity as related to Water Use Efficiency (WUE) and Water Productivity (WP) in Greece is analyzed by means of: the hydrological aspects and agronomic management strategies, the eco-physiological aspects and sustainability including social, economic, environmental and political measures. Furthermore, the initiatives and activities to improve Water Use Efficiency and to increase food production by using less water are reported.