Background: Diagnostic radiology by the use of ionizing radiation plays a main contribution in the collective dose of human population. Knowing the radiation dose received by patients during a radiological examination is essential to prevent the excess health risk of exposure. Objectives: The aim of this study was to estimate the collective dose and calculate the cancer risk probability due to common radiological procedures in four radiology imaging centers of Iran. Patients and Methods: Four hundred seventy patients who underwent different radiological examinations including the skull, chest, abdomen, pelvis, lumbar, cervical and thoracic regions in four radiology centers of Hamadan, Iran were studied. The patients' entrance surface dose (ESD) was measured, and eventually, the effective dose (ED) was calculated. These parameters were compared with the reported values and international standard levels. Finally, the risk of cancer was determined by two different methods proposed in international commission on radiological protection (ICRP) 103. Results: Mean values of ESD for chest, abdomen, pelvis, lumbar region, skull, cervical and thoracic regions were 0.43 ± 0.09, 2.51 ±0.19, 2.47±0.02, 3.21±0.17, 2.15±0.11, 1.35±0.15, and 2.51±0.19 mGy, respectively. The mean values of ED were 0.05, 0.33, 0.25, 0.42, 0.02, 0.05 and 0.24 mSv, respectively for these organs. The cancer risk probability as a function of cumulative dose was 0.20, 1.21, 0.08, 1.32, 0.01, 0.01 and 0.04 (person - Sv x 5% per Sievert) for the interested organs, respectively. The risk of cancer as a function of age and sex for male patients was 0.86, 1.47, 0.59, 0.02, 0.16, 1.96 and 0.76 (in 103 person) for the bladder, colon, liver, thyroid, esophagus, lung and stomach, respectively. These values were, 0.34 (or 2.12), 0.73 (or 4.47), 0.98, 0.43, 0.72, 0.19, 0.25, 0.26 and 1.20 (in 103 persons) for breast, lung, bladder, ovary, colon, liver, thyroid, esophagus and stomach for females. Conclusion: Results show that the estimated health risk based on ICRP health risk of 500 cases per 10000 person - Sv (5% per Sievert) was in total about 2 cases for seven examinations in 2016. Risks of cancer as a function of age and sex for male patients were higher for lung and colon cancers and for females, it was higher for breast and lung cancers. [ABSTRACT FROM AUTHOR]