Different samples of water, indoor air and soil gas have been collected from Islamabad (33°38′N, 73°09′E, altitude of 1760 ft.), the capital of Pakistan and Murree (33°53′N, 73°23′E, altitude of 7323 ft.), lying on a geological fault line and are analysed for the estimation of mean effective dose through radon concentrations by using RAD-7, a solid state α-detector. The variation of radon concentration in water, indoor air and soil gas in Islamabad region ranges from 25.90–158.40 kBq m⁻³, 43.26–97.04 Bq m⁻³ and 17.34–72.52 kBq m⁻³, having mean values 88.63 kBq m⁻³, 70.67 Bq m⁻³ and 45.08 kBq m⁻³_, respectively. It ranges from 1.64–10.20 kBq m⁻³, 18.48–42.08 Bq m⁻³ and 0.61–3.89 kBq m⁻³ with mean values 4.38 kBq m⁻³, 28.63 Bq m⁻³ and 1.70 kBq m⁻³_, respectively in Murree and its surroundings. The total mean annual effective doses from water and indoor air of Islamabad and Murree regions are 2.023 and 0.733 mSv a⁻¹, respectively. These doses are within the recommended limits of the world organisations.