Small 5mm ground glass nodules in the lungs are mostly caused by benign diseases and most of them are not serious; however, they can be malignant and are more serious if they are malignant. Lung nodules can be caused by a wide range of benign and malignant lung diseases, with different nodule sizes, densities, and morphologies, and varying degrees of severity. A 5mm ground glass nodule is a small nodule, mostly caused by benign diseases such as pneumonia, tuberculosis, etc. The nodule has clear boundaries, uniform density and smooth edges, and after regular and effective anti-infection and anti-tuberculosis treatments, the inflammatory nodule will gradually shrink or even disappear completely, which is generally not serious. If the 5mm ground-glass nodule does not improve respiratory symptoms such as coughing and sputum during the above treatment or regular follow-up, but instead the nodule continues to increase in size, with rough and lobulated edges, infiltrative growth or pulling on the pleura, the malignant nature of the nodule should be highly suspected, and then it will be more serious. Surgery is needed as soon as possible. Patients with 5mm ground glass nodules in the lungs are advised to consult their specialists and follow up, examination or treatment as prescribed by their doctors.