Whether a small nodule of 4mm in the right upper lung is serious or not should be analyzed depending on the specific situation. Usually, for nodules smaller than 5mm, the possibility of benign lesions is greater, especially 4mm nodules, usually without special treatment, patients are instructed to review regularly, usually about 6 months to 1 year, dynamic observation of the nodules have changes. If there is no obvious change, the disease is not serious, and the lung CT can be reviewed once a year in the future, but if the right upper lung nodule is gradually increasing in size through the six-month review, or the nodule is localized with the formation of vacuolar signs, then attention should be paid to it. When the morphology of the nodule changes, it is necessary to pay attention to the possibility of malignant tumor, and it should be closely observed, especially when the nodule gradually increases more than 8mm, and the edge of the local area is not smooth, which is a serious problem, and the patient needs to improve the examination as early as possible, and perform thoracoscopic resection as early as possible if necessary, to avoid the development of lung cancer.