Natural radioactivity and radon concentration were studied in drinking water samples from Baling area, Kedah, Malaysia, using HPGe and RAD-7 detectors, respectively. Average concentrations obtained for 226Ra, 232Th, 40K and 222Rn were 44.2 ± 3.9, 38.1 ± 5.0, 140.9 ± 10.6 mBq l−1 and 5.7 ± 0.68 Bq l−1, respectively. Cumulative annual effective doses due to ingestion of 226Ra, 232Th, 40K and 222Rn for infants, children and adults were estimated to be 13.77, 2.857 and 2.581 μSv y−1, respectively. Average annual effective doses due to inhalation of radon released in the air during consumption and ingestion of drinking water were separately estimated to be 15.2 and 1.2 μSv y−1, respectively. A positive correlation (R2 = 0.87) was observed between 222Rn and 226Ra determined by RAD-7 and HPGe detectors, respectively. In this study, the estimated annual effective doses due to ingestion of 226Ra, 232Th, 40K and 222Rn for infants, children and adults were found to be below the World Health Organization (WHO) recommended limits of 0.1 mSv y−1.