Introduction: Alpha particle emitters are extremely destructive and detrimental to the human body, if inhaled or consumed, swallowed, or absorbed into the lungs or bloodstream. 222Rn is one of alpha-particle emitter. Material and Methods: we studying the concentrations of radon gas (222Rn) in blood samples of 10 cancer patients and 6 control measured using CR-39 detector. The samples were collected from Babylon oncology center. Results: The highest concentration of radon for cancer was 267.22 Bq/m3 , while for control was5.98 Bq/m3 . The lowest concentration of radon for patient was 16.55 Bq/m3, while for control group was 2.77 Bq/m3. Conclusion: These study concluded the level of radon concentration increased of cancer patient compare with control group, also these study concluded the level of radon in center of Babylon city higher than of rural of Babylon.