Radon is a natural radioactive gas that is exhaled from soil and building materials, and tends to concentrate in places with low ventilation. According to UNSCEAR, 52% of the natural radiation dose received by humans is due to radon and most of the exposure occurs indoors. According to WHO, diseases such as lung cancer can be caused by inhaling radon. Using LR115 and CR39 detectors in naked mode, radon concentration was measured in two rooms in a house north of Lima. These were differentiated by the ventilation, during the measurement one remained closed and the other kept a window open. The measurements were taken during the months of June and July 2019. The detectors then underwent an etching process at the Laboratory of Nuclear Fingerprints of the Pontificia Universidad Cat lica del Per (PUCP). The reading of the traces revealed in the CR39 was done with the LEICA microscope and for the LR115 the POLITRACK system was used. According to the results with LR115, the radon concentration shows an oscillating behavior that decreases as the distance from the wall increases.