In 2013, an extensive study was performed in a total of 117 locations in Izmir province and indoor radon levels were measured using the alpha track etch integrated method with LR-115 detectors. As the maps are more practical to interpret the results of radiological survey' he distributions of indoor Rn-222 activities in four most densely populated districts of Izmir were mapped in detail. It is seen that the estimated average radon concentration level (210 Bq m(-3)) determined in Izmir province was almost three times higher than the mean value for Turkey (81 Bq m(-3)). Exposed annual effective dose equivalents for Izmir province were estimated in the range of 0.7 to 2.3 mSy year(-1) with a mean of 5.3 mSv year(-1). In this study, it is pointed out that indoor radon concentration was affected by the age f the building and height above the ground.