The present work is a comprehensive evaluation of drinking water quality from various regions of Greece. The physicochemical parameters investigated were conductivity, total dissolved solids and pH, as well as related to the treatment of drinking water such as chloride, potassium, calcium, magnesium and sodium, heavy metals (including cadmium, copper, lead, chromium and nickel), anions and cations such as fluoride, bromide, nitrates, nitrites, ammonium, sulphates and phosphates, as well as dissolved organic carbon. The parametric values set in accordance with the Directive 98/83/EC were exceeded in the cases of lead (in 2.7% of the samples analysed), chloride (2.4%) and nickel (2.1%). Ammonium, sodium, fluoride, sulphates, nitrates and conductivity were lower than the upper limits by 2% of the total number of samples analysed. The majority of problems were identified in the Cyclades islands, particularly those characterized by scarcity of water resources. The main problems related to drinking water quality are associated with the conditions of the water supply networks, the pollution of 'parent' water and in particular the contamination of groundwater with pollutants of both anthropogenic and natural origin, as well as the intrusion of seawater in aquifers.