A survey study on radioactivity in drinking water from three lakes in the region of Attika in Greece is in progress since 2004. The measurement of gross alpha and gross beta activity is used as a screening method. All the values of alpha and beta activity in the selected water samples were lower than the permissible limit for drinking water consumption, 1.0 and 0.1 Bq/L respectively. The determination of gamma-emitters was performed by use of gamma spectrometry and the determination of alpha-emitters by use of alpha-spectrometry. The values of U-238 and U-234 vary between 0.91 to 17.27 and 2.13 to 22.01 mBq/L respectively. The U-234/U-238 activity ratio varies between 1.12 and 2.40.