Solid lung nodules are imaging findings in the lungs, corresponding to cystic changes and ground glass nodules. Solid lung nodules are mostly benign, commonly found in tuberculosis, inflammatory pseudotumor, etc.; they may also be malignant, such as early lung adenocarcinoma. 1. Tuberculosis: after infected with tuberculosis, tubercle bacillus enters into the lungs and causes damage, forming granulomatous nodules, showing round solid density shadow, often accompanied by exudation and adhesion. In the case of hematogenously disseminated TB, a large number of evenly distributed, uniformly dense granular shadows may appear in both lungs. It can be treated with anti-tuberculosis therapy such as isoniazid and rifampicin. 2. Inflammatory pseudotumor: Inflammatory pseudotumor is a kind of chronic non-specific inflammation, not a tumor, mostly related to immune response. Inflammatory pseudotumor is mostly manifested as a single round or round-like solid nodule with smooth edge. Solid nodules caused by inflammatory pseudotumor are treated by anti-infection therapy such as glucocorticoid. 3. Early stage lung adenocarcinoma: lung adenocarcinoma is a common lung malignant tumor. Early stage confined lung adenocarcinoma is mostly glassy nodules, but some of them can also be solid lung nodules, with uneven density of lesions and typical manifestations such as burr sign and pleural indentation sign. In conclusion, it is recommended to consult doctor in time to find out the cause of lung solid nodules and receive regular treatment. Benign solid lung nodules may become malignant, so regular medical checkups are recommended.