Background: There is a rapid increase worldwide in the consumption of mineral waters which may contain different level of radioactive elements, especially ²²⁶Ra, in addition to varying amounts of beneficial salts. Therefore, a comprehensive study was planned and carried out in order to determine concentration of ²²⁶Ra natural radionuclide in bottled mineral waters that commercially available in Marmara Region of Turkey. Materials and Methods: The method used for ²²⁶Ra concentration analysis bases on the measurement of Radon (²²²Rn) coming from ²²⁶Ra dissolved in the water. The measurements were performed using RAD 7, a solid state α detector, with RAD H₂O accessory manufactured by DURRIDGE COMPANY Inc. Results: The ²²⁶Ra concentration in mineral waters was found to vary from <0.074 to 0.625 Bql^-1 with an average value of 0.267 Bql^-1.The committed effective doses due to ingestion of 226Ra from the one year consumption of these waters were estimated to range from 10.8 to 90 µSvy^-1, from 9 to 75 µSvy^-1 and from 3.15 to 26.25 µSvy^-1, for infants, children and adults, respectively. Conclusion: The results obtained in this study indicate that the committed effective doses are below the WHO (World Health Organization) recommended reference level of 100 µSvy^-1.