OBJECTIVE: To improve the CT diagnosis of isolated lung lesions. METHODS: A retrospective analysis of 54 misdiagnosed cases diagnosed by multi-row spiral CT (MSCT) and confirmed by surgical pathology or follow-up was performed. A controlled study of MSCT signs and pathology was performed in two groups, benign and malignant, to analyze the relationship between lesion size and signs. RESULTS: In the benign group, 21 cases were misdiagnosed as peripheral lung cancer, including 16 cases of inflammatory or focal organized pneumonia (FOP), 3 cases of tuberculosis, 1 case of cryptococcal infection, and 1 case of sclerosing hemangioma. One case of adenomatoid hyperplasia (AAH) was found. The incidence of density inhomogeneity, vacuolar sign/bronchial inflation sign, typical lobulation, short fine burr, spiny protrusion and typical pleural indentation (PI) was higher in the malignant group than in the benign group, and the probability of density inhomogeneity, vacuolar sign/bronchial inflation sign was statistically significant between the two groups (P < 0.05), and the maximum diameter of lesions >3 cm and ＜There was a difference in the occurrence rate of MSCT signs for lesions >3 cm and <3 cm. Conclusion: Uneven density and vacuolation signs suggest malignancy, and when the maximum diameter of the lesion is >3 cm, lobulation or spiculation may suggest malignancy, and the correct grasp of these signs can reduce the misdiagnosis rate.