Objective To study the diagnostic value of SPECT/CT and PET/CT in lung cancer and bone metastasis. Methods 240 cases of patients with suspected lung cancer from April 2015 to April 2018were treated with 18F-FDG SPECT/CT and 18F-FDG PET/CT, among which 213 cases were confirmed by surgery or other examinations. The clinical comprehensive diagnosiswas taken as gold standard to compare the diagnostic value of the two methods for the primary lung cancer lesions and bone metastases and the detection rate of different volumes of lung cancer lesions. Results The sensitivities of 18F-FDG SPECT/CT and 18F-FDG PET/CT were 87.79% and 92.96%in the diagnosis of primary lung cancer, and the specificities were 92.60% and 96.30%, and the accuracy rates were 88.33% and 93.33%, and the Kappa values of consistency test were 0.579 and 0.728 respectively. The sensitivities for diagnosis of bone metastasis of lung cancer were 93.21% and 94.54%, and the specificities were 89.71% and 94.12%, and the accuracy rates were 92.86% and 94.49%, and the Kappa values of consistency test were 0.679 and 0.745respectively. The detection rate of primarylung cancer lesions with diameter≤1cm by 18F-FDG SPECT/CT was lower than that of 18F-FDG PET/CT (P<0.05), and there was no significant difference in the overall detection rate between the two groups (P>0.05). Conclusion 18F-FDG SPECT/CT and 18F-FDG PET/CT both have high accuracy rate in the diagnosis of primary lesions and bone metastasis of lung cancer, and the diagnostic value of 18F-FDG PET/CT is better than that of 18F-FDG SPECT/CT, and it has obvious advantages in detection rate of minute lesions, but 18F-FDG SPECT/CT has a wider range of applications and a relatively lower price, thus it is suitable for clinical routine development.