Pulmonary nodules are round-like or irregular shaped lesions ≤3 cm in diameter in the lungs, which are imaged as hyperdense shadows. Small nodules are the smaller diameter pulmonary nodules with increased density shadows of <10 mm or less in diameter within the lung detected by CT scan. There are more clinical diseases that present as small pulmonary nodules, such as inflammation, bleeding, infection, allergy, tuberculosis, and tumor, etc., which can manifest as hyperdense shadow in the lung. Most benign nodules have clear borders and are smooth, with relatively uniform internal density or calcification, and some nodules can be slowly absorbed and reduced. However, most malignant nodules originate from distant metastatic tumors or primary lung tumors and often have malignant manifestations such as burr, lobulation, pleural crinkling, inflatable bronchial signs or vascular collection signs, requiring clinical intervention and, if necessary, surgery. The site of nodule occurrence can occur on the left side or on the right side. They can occur in the upper or lower lobe of the lung, and the location of the nodule in the lower left lung is only different compared to the other lobes of the lung, and does not affect whether the nodule is benign or malignant. It is important to analyze each nodule on a case-by-case basis. If in doubt, you can go to a specialized medical institution to see a thoracic surgeon or imaging department to have the film read by a senior physician to determine the nature of the lesion so as not to miss the best time for treatment.