Radon levels were measured in 59 water samples of rural and urban places of Bangalore city following procedures of standardized techniques. Though water level of radon above 100 Bqll −1 of WHO is ascribed to causes of lung cancer and leukaemia, very low levels were found in different urban and rural places, but urban-rural gradient observed significantly higher urban levels than rural levels. Correlation between depth of water sampled and radon levels estimated indicates that in urban places, lower water depth is related to higher radon levels, while it is vice versa in rural. It is due to more water use for rural agriculture and more urban water pollution and granite quarries. In comparison to other countries, it is observed that water radon levels are at wide ranges from the lowest to the highest estimated with different techniques and differ due to types of water, soil, rocks and sampling season.