The size of lung nodules is not related to whether one has lung cancer or not, but also needs to be analyzed in combination with the distribution, density and morphology of the nodules to facilitate the diagnosis of lung cancer, lung misshapen tumor and other diseases. Lung nodules are focal round dense shadows of various sizes, with clear or blurred edges and a diameter of less than or equal to 3cm on lung images, which can be classified as benign and malignant. However, to determine how many mm of lung nodules are designated as lung cancer, it is necessary to analyze the results in combination with the distribution, density, morphology and other aspects of the lung nodules, and the size of the lung nodules alone cannot diagnose whether it is lung cancer or not. If the examination reveals that the lung nodule is irregularly lobulated and there are signs such as radioactive burrs and eccentric thick-walled cavities in the periphery, regardless of the size of the nodule, it is usually highly suspected to be lung cancer, which belongs to malignant tumor diseases. If the examination results show smooth and neat edges of lung nodules with popcorn-like calcification, it is mostly considered to be lung malignant tumor, which belongs to benign tumors. Therefore, for patients who are examined for the presence of lung nodules, further relevant examinations need to be done in order to clarify the specific cause of the disease.