Abstract: Objective: To evaluate the application value of 18F-FDG PET/CT combined with HRCT in diagnosing pneumonia type of bronchioloalveolar carcinoma(PTBAC). Materials and Methods: The 18F-FDG PET/CT images of 26 cases with pathologically confirmed PTBAC were studied. Fifteen of the 26 cases were followed up after 0~3 days by HRCT study. The diagnostic accuracy rate of 18F-FDG PET/CT combined with HRCT were analyzed. Results: According to 18F-FDG PET/CT imaging, definite diagnosis of malignant was made in 9 cases, no exclusion of malignancies in 13 cases, and definite diagnosis of pulmonary inflammation in 4 cases. The diagnostic accuracy rate of 18F-FDG PET/CT imaging was 34.6%. The misdiagnosis rate of 18F-FDG PET/CT was higher. Associating 18F-FDG PET/CT with HRCT, 13 of 15 cases were diagnosed as malignant tumors. Pulmonary inflammation was diagnosed firstly in 1 case by PET/CT, and then definite diagnosis of malignancy was confirmed by HRCT. In addition, the other one case of malignant tumor was analyzed as pulmonary inflammation by PET/CT and HRCT. However, 18F-FDG PET/CT displayed metastasis during the delay scanning, which was approved by pathology. Based on 18F-FDG PET/CT and HRCT results, 15 cases were diagnosed correctly. Conclusion: PTBAC displays a variety of characteristics in 18F-FDG PET/CT and HRCT. Combining 18F-FDG PET/CT with HRCT is reasonable and practicable for PTBAC diagnosis, which may be due to the synergistic effect on diagnosing PTBAC and can greatly improve the diagnostic accuracy.