Radon ((222)Rn) is a tasteless, colourless and odourless radioactive noble gas, responsible for approximately 50% of radiation from natural sources. Being highly soluble in water, radon in water sources is also a major public health concern and is still an active research area. This paper presents the results of radon concentration measurements in thermal water samples from Cekirge region of the city of Bursa, rich in geothermal waters located in the northwest part of Turkey. The radon activity concentrations in 36 thermal water samples were determined by using AlphaGUARD PQ 2000PRO radon gas analyser. AlphaGUARD is an ionizing chamber which measures radon via alpha spectrometric techniques. It is found that the concentration ranged from 2.513 +/- 0.286 to 82.553 +/- 1.919 Bq.L(-1) for radon. The doses delivered to the users during treatment were also calculated and found to be in the range of 0.36 nSv to 11.89 nSv per treatment.