Radon and its progeny are major contributors that deteriorate the indoor air quality and are the major source of radiation dose received by general population of the world. Keeping this in mind the environmental monitoring of radon-thoron and their progeny in dwellings of district Mohali, Punjab, India has been carried out. The radon-thoron twin dosimeter cups were used for the study. The study of the exhalation rate of the soil samples of Kharar, Kurali and Derabassi of the district Mohali and the sand samples available from the study area has also been carried out for the comparison purpose using can echnique. The aim of the study is the possible health risk assessment in the dwellings of this particular region for which data is not available in literature. The indoor radon concentration varied from 22.8 ± 0.7 Bq/m3 to 45.0 ± 2.2 Bq/m3 with an average of 33.7 Bq/m3 while the thoron concentration in the same dwellings varied from 1.7 ± 0.1 Bq/m3 to 27.6 ± 1.2 Bq/m3 with an average of 12.8 Bq/m3. Annual dose received by the inhabitants in the dwellings under study varied from 0.64 to 1.64 mSv with an average of 1.19 mSv. The radon mass and surface exhalation rates of the soil samples varied from 0.32 to 2.6 mBq/kg/h with an average of 1.36 ± 0.2 mBq/kg/h and from 7.3 to 58.2 mBq/m2/h with an average of 28.3 ± 5.1 mBq/m2/h respectively.