Objective To investigate the total examinations of conventional X-ray diagnosis and CT diagnosis of radiation diagnosis and treatment institutions,in order to explore the distribution characteristic of radiological diagnosis frequency and diagnostic patients,and to estimate the application frequency of medical X-ray diagnosis in Heilongjiang province.Methods The questionnaire was sent to all radiation diagnosis and treatment institutions in forms of public document issued by the administrative department of health and family planning of Heilongjiang province.Basic situations and patient numbers of conventional X-ray diagnosis (interventional diagnosis not included) and CT diagnosis in 2016 were collected and summarized combined with sampled on-site verification.The application frequency of medical X-ray diagnosis was obtained using permanent resident population in Heilongjiang province in 2016.Results Totally 1 645 medical radiation institutions were investigated,including 81 tertiary hospitals,359 secondary hospitals,808 primary hospitals or unrated medical institutions,and 397 private dental clinics.The examinations of conventional X-ray diagnosis and CT diagnosis were 7 706 050 and 7 063 734,respectively.The application frequency of conventional X-ray diagnosis and CT diagnosis was 200.9 and 184.1 examinations per 1 000 population,respectively,and varied from 98.0 to 274.7 in different areas.The ratio of examinations in public medical institutions to that in private medical institutions was 7.47 ∶ 1.Conclusions 50％ of the total radiological diagnosis were made in tertiary hospitals,and only 13％ were made in medical institutions below primary in Heilongjiang.Meanwhile,although the number of public and private medical institutions was at the same scale,the total examination of radiological diagnosis in public medical institutions was 7 times of that in private medical institutions.The application frequency of conventional X-ray diagnosis and CT diagnosis in Heilongjiang province in 2016 was similar to that of Jiangsu province in 2015.