3mm solid nodule in the upper lobe of the left lung, consider observation and follow-up, surgical treatment and so on. 1. Observation and follow-up: 3mm lung nodule is a small nodule, generally considered benign lesions, there are no uncomfortable symptoms, such as cough, chest pain, dyspnea, etc., generally do not need special treatment, follow-up observation can be, pay attention to the size of the nodule, morphology, density changes. 2. Surgery: If the nodule increases in size and solidity, the solid component in the middle of the ground glass increases, and there are mixed ground glass nodules with burr and lobulation signs, it suggests the possibility of malignant changes, and it is necessary to carry out bronchoscopic biopsy or puncture biopsy, and if it is cancerous, it is necessary to carry out surgery as early as possible. If the nodule is cancerous, surgery should be performed as soon as possible. 3mm solid nodule in the upper lobe of the left lung is recommended to go to the hospital for examination, to clarify the specific type, and then follow the doctor’s instructions for treatment in conjunction with the clinical symptoms.