[en] The aim of this work was to study the long-lived Ra isotopes, ²²⁶Ra and ²²⁸Ra, natural distribution in mineral and spring waters from Caxambu (MG) and Aguas de Lindoia (SP) water parks. In Caxambu mineral waters it was observed ²²⁸Ra activity concentrations slightly higher than those of ²²⁶Ra. The elevated content of carbonates and bicarbonates of these waters can result in an increased solubility of the both Ra isotopes and may play an important role for the fate of ²²⁸Ra and its equilibrium distribution between solid and liquid phases. In Caxambu Thermal Spa, arithmetic mean activities ranged from 83 mBq L^-1 to 3599 mBq L^-1 and from 60 mBq L^-1 to 4481 mBq L^-1 for ²²⁶Ra and ²²⁸Ra, respectively. The highest ²²⁶Ra activity was found in Venancio Spring, while the maximum ²²⁸Ra activity value was determined in Ernestina Guedes. ²²⁸Ra/ ²²⁶Ra activity ratios varied from 0.079 (Conde D'Eau and Princesa Isabel Spring) to 4.2 (Mairink II Spring). In Aguas de Lindoia, arithmetic mean activities ranged from 4.6 mBq L^-1 to 41 mBq L^-1 and from 30 mBq L^-1 to 54 mBq L^-1 for ²²⁶Ra and ²²⁸Ra, respectively. The maximum ²²⁶Ra activity concentration was found in the bottled mineral water Sao Jorge, while the higher ²²⁸Ra activity concentration was determined in Santa Filomena Spring (public station 2). ²²⁸Ra/ ²²⁶Ra activity ratios varied from 1.2 (bottled mineral water Sao Jorge) to 9.1 (bottled mineral water Jatoba 1). This work also performed the dose assessment due to the ingestion of ²²⁶Ra and ²²⁸Ra in Caxambu and Aguas de Lindoia mineral and spring waters. The committed effective doses were estimated by using a conservative dosimetric model and taking into account the results over a lifetime (70 years) following intake of both long-lived Ra isotopes. The results from this radiological evaluation showed that the guidance committed effective dose level of 0.1 mSv y-1 recommended by World Health Organization was exceeded in almost all samples studied in Caxambu, except for Viotti Spring, Dom Pedro Spring and Dona Leopoldina Spring. In Aguas de Lindoia and Lindoia, the highest committed effective doses estimated were 8.4 10-3 mSv y-1 for the intake of ²²⁶Ra (bottled mineral water Sao Jorge) and 2.6 10-2 mSv y-1 for ²²⁶Ra (Santa Filomena spring - station 2). Both values are below the limit recommended by World Health Organization. The maximum committed effective doses per year obtained in this work were 7.4 10-1 mSv y-1 for ²²⁶Ra (Venancio Spring) and 2.2 mSv y-1 for ²²⁸Ra (Ernestina Guedes Spring). Considering the case of '2²⁶Ra intake via mineral water, the dose obtained represents less than 31 % of the average effective dose attributable annually from natural background radiation. However, in the case of ²²⁸Ra the annual committed effective dose limit recommended by ICRP (considering all sources of radiation exposure for the world population) was exceeded not only in Ernestina Guedes Spring, but also in Beleza Spring. (author)