BACKGROUND: Ionizing radiation is a group 1 carcinogen according to the IARC(International Agency for Research on Cancer) classification. With the development of the radiation related industry, the number of radiation exposed workers has been increasing. There have been several reports on AML(Acute Myeloid Leukemia) on exposure to ionizing radiation; however, there are no reports of occupational malignant lymphohematopoietic disease related to non-destructive inspection. CASE REPORT 1: A 35-years-old male, who had worked for 10 years in non-destructive inspection, was diagnosed with myelodysplastic syndrome. He worked 8 hours a day, for three weeks per months, where he was exposed to 192Ir and 60Co radiation sources. Because he had not worn a film badge for monitoring his radiation exposure dose, the accurate exposure dose was not reported. The estimate exposure dose calculated via a chromosomal study was 1.20 Gy, which exceed the dose limits of Korean radiation dose standards, which are 50 and 100 mSv annually and quinquennially respectively. CASE REPORT 2: A 26-years-old male, who had worked for 2.5 years in the same company was also diagnosed with myelodysplastic syndrome. CONCLUSION: Non-destructive inspection is the main source of ionizing radiation in the workplace, which could be the cause of malignant lymphohematopoietic diseases. Therefore, more practical plans and guidelines are needed to prevent non-destructive inspectors from workplace radiation exposure.