Background: It is considered that if radon gas is inhaled and ingested, it is the primary health risks for lung and stomach cancers. This paper presents the measurement results of radon ac vity concentra ons both residen al tap water and dam water for Kastamonu city Centre-Turkey. Materials and Methods: The radon ac vity concentra ons of water samples collected from 60 tap waters at four loca ons and 12 dam water of study area were determined. Radon concentra ons were measured using the professional radon monitor AlphaGUARD PQ2000 PRO (Genitron Instruments). , respec vely. The annual effec ve doses were calculated for the inhala on of radon released to air when water is used and the inges on of drinking water. The mean values for inhala on and inges on were found to be 0.1266 μSv y -1 and 0.0105 μSv y -1 , respec vely. For the radon exposure from inges on, the annual effec ve doses were calculated for infants, children, and adults, separately. Conclusion: When the results compared with the interna onally recommended safe limits, the tap waters of Kastamonu city Centre is safe for drinking purposes in terms of radon ac vity concentra ons.