Pulmonary nodules are small, focal, round-like shadows with increased density on imaging that may be solitary or multiple, without pulmonary atelectasis, hilar enlargement, or pleural effusion. Isolated pulmonary nodules have no typical symptoms and are often single, well-defined, hyperdense, soft tissue shadows ≤3 cm in diameter surrounded by air-containing lung tissue. Small nodules in the lung are not equal to early lung cancer. Many diseases in the lung can form nodules, benign ones such as inflammation, tuberculosis, mycobacteria, subsegmental atelectasis, hemorrhage, etc. Thus the possible diagnoses of small nodular lesions within the lung can be diverse. Benign ones include inflammatory pseudotumors, malignant tumors, tuberculosis globules, fungal infections, sclerosing pneumocytoma, etc. The malignant ones may be primary lung cancer or metastatic cancer in the lung. Some benign lesions, of course, may also turn malignant after a long period of time. The nature of lung nodules should be considered in conjunction with the imaging pattern of the nodules, clinical manifestations, and further examination or surgical treatment if necessary.