In the present work, radon concentrations were measured in surface and underground water samples in Faridabad District of Southern Haryana, India using an active radon monitor based on alpha scintillation technique and results have been intercompared. The average radon concentration in the underground water samples was observed to be 4 times higher than in the surface water samples. The estimated annual effective dose varied from 5.7 to 58.5 μSvy⁻¹ with an average of 24.2 μSvy⁻¹ for underground water samples and 1.1 to 12.5 μSvy⁻¹ with an average of 6.7 μSvy⁻¹ for surface water samples. The estimated annual effective dose for both type of samples was found to be less than 0.1 mSvy⁻¹, which is the safe limit as suggested by World Health Organisation and EU Council.