Introduction One of the central questions in radiological protection is the magnitude of the risks from low doses of radiation, related to the justification and optimization of the diagnostic medical exposures. Therefore, the aim of this study was to estimate the cancer incidence and mortality risks in children of different ages, sizes, and ethnicities undergoing computed tomography examinations. Materials and Methods In this study, the risk estimations were performed, using the organ dose data of 16 pediatric voxel phantoms obtained in our previous publications. In addition, we employed the risk models recommended by the committee of biological effects of ionizing radiation for all solid cancers, leukemia, and cancers of several specific sites. Linear interpolation was also applied for the risk estimations of different ages. Results According to the results of this study, there are significant differences between the cancer risks for some organs even in the phantoms of the same age. Therefore, it was concluded that using the reference data for all children with anatomical discrepancies would lead to under- or overestimation of the risk values. In addition, only the amount of dose cannot be the appropriate representative of the risk, and parameters like size, age, and gender might have direct impacts on cancer incidence and mortality risks. Conclusion The findings of the current study are useful to update the information about the individual and the long-term collective public health risks.