Objective To estimate the lifetime attributable risk (LAR) of thyroid cancer due to radiation in individuals undergoing chest computed tomography (CT) examinations. Methods Scanning parameters were retrospectively collected from DICOM files of 660 individuals who underwent chest CT scans between 2022 and 2024. Individuals were stratified by age and sex. Size-specific dose estimates were calculated using a formula based on the volume CT dose index for each individual. The radiation doses received by the thyroid were estimated. The cancer risk prediction model from the US National Academy of Sciences report on the Biological Effects of Ionizing Radiation was referenced to predict the LAR of thyroid cancer. Results The LAR of thyroid cancer for males/females was 25.170/100 000 and 140.177/100 000 in the ≥ 0 and<5 years of age group, 21.779/100 000 and 102.498/100 000 in the ≥5 and <10 years of age group, 22.987/100 000 and 128.934/100 000 in the ≥10 and <15 years of age group, and 4.979/100 000 and 12.490/100 000 in the ≥15 years of age group. A Spearman correlation analysis showed that age was highly correlated with volume CT dose index, size-specific dose estimates, radiation dose received by the thyroid, and thyroid cancer LAR, with correlation coefficients of 0.887, 0.737, 0.737, and −0.41 (P<0.01), respectively. Sex was correlated with radiation dose received by the thyroid and thyroid cancer LAR, with correlation coefficients of 0.179 and 0.441 (P<0.01), respectively. Conclusion Chest CT scan leads to an increased LAR of thyroid cancer. Appropriate protective measures for the thyroid should be considered during chest CT scan to reduce the impact of radiation on the thyroid.