This paper presents the results of radon ((222)Rn) concentrations in drinking water and river water. In this respect, water samples were collected in the city of Amasya, inner parts of the Median Black sea region in Turkey and the Yeşilirmak River flowing through Amasya city centre. It was found that the concentrations in tap water, spring water and the Yeşilirmak River water in Amasya ranged from 0.42 +/- 0.14 to 2.4 +/- 0.32 Bq l(-1), 0.39 +/- 0.19 to 1.17 +/- 0.21 Bq l(-1) and 0.28 +/- 0.04 to 1.08 +/- 0.30 Bq l(-1), respectively. From these data, the average effective dose equivalent from radon in tap water has been estimated as 5.87 microSv y(-1).