A 5mm ground-glass nodule is not serious if it is an inflammatory lesion; it is more serious if it is caused by a malignant tumor. Round-like shadows ≤3 cm in chest CT are called pulmonary nodules, which can be divided into ground-glass nodules and solid nodules according to their composition, and ground-glass refers to cloudy, slightly dense shadows. Ground glass nodules also include pure ground glass nodules and mixed nodules (both ground glass and solid components). Pure ground glass nodules have a lower risk of malignancy, while mixed nodules have a higher probability of malignancy. Ground glass nodules can be caused by pneumonia due to bacterial and viral infections in the lungs, as well as tuberculosis and sarcoidosis, or by malignant tumors such as lung cancer and metastatic carcinoma. The risk of malignancy of ground-glass nodules is also related to the size of the nodules. Generally, nodules <5mm are mostly benign, and nodules >8mm have a 20% or more chance of being malignant. Therefore, it is more likely that a 5-mm ground-glass nodule is the result of a benign disease such as inflammation in the lungs, but the risk of lung cancer cannot be ruled out. Patients are advised to consult a specialist for a comprehensive analysis based on the shape, composition and calcification of the nodule, and follow the doctor’s instructions for further examination and treatment.