Recently, many friends, colleagues and patients have asked whether there is any harm in doing radiological examinations (mainly general radiographs and CT, as well as nuclear medicine examinations and treatments). There are 2 types of radiation here, one is ionizing radiation, referring to ordinary films and C T. They are not harmful, but cannot be done repeatedly within a short period of time. The second is nuclear medicine examination and treatment, which is more dangerous than the former, because it has radionuclides into the body, and it takes a period of time for the body to metabolize to eliminate. Generally speaking, during the radiological examination and treatment, the problem should be analyzed from a dialectical point of view, because of the need of disease diagnosis and treatment, which has to be carried out, and if it has to be done repeatedly in a short period of time, blood must be drawn regularly to check the white blood cells and platelets, for example, during radiotherapy for malignant tumors; if it is not medically necessary, it should be avoided as much as possible. Both clinicians and patients should have should have this awareness.