The differences between multiple nodules and solitary nodules in the lungs are different etiologic factors causing the nodules, different degrees of severity, and different sizes and natures of the nodules. 1. Different causes of nodules: Multiple nodules in the lungs are often seen in infectious diseases of both lungs, such as chronic obstructive pulmonary disease, chronic bronchitis, bronchiectasis, and long-term smoking, exposure to dust, etc. Repeated inhalation of hazardous substances and dust can easily lead to the production of multiple nodules in both lungs. Lung nodules are mainly benign lesions, such as benign tumors in the lungs or the scar left after recovery from tuberculosis, but malignant possibility is not excluded. 2. Different degrees of severity: the malignant possibility of multiple nodules in the lungs is small, so the degree of severity is light, but the possibility of malignancy is not excluded, such as metastatic tumors in the lungs can be manifested as multiple nodules in the lungs. If the imaging of single nodules in the lungs is ground glass, burr-like changes or mixed nodules, it is necessary to determine whether the nodules are malignant or not according to the size of the nodules. Any malignant lesion is serious and should be treated early. 3. The size of the nodule and the nature of the nodule: multiple nodules in the lungs are generally of uniform size and density, which can be benign or malignant. If the single lung nodule is larger than 1cm, it is necessary to give chest high-resolution CT and pathological biopsy to exclude the possibility of malignant tumors as early as possible. If lung nodules are found, one should go to the hospital for a more comprehensive examination and treatment under the guidance of a specialist.