A 12mm lung nodule is usually not a large nodule, but requires active medical attention and regular chest CT and other tests as prescribed by your doctor. Most of the lung nodules are confined, round-like, with increased density shadows on imaging, and may be single or multiple. Clinically, nodules with a diameter of less than 5mm are categorized as micronodules, lung nodules with a diameter of 5 to 10mm are categorized as small nodules, nodules larger than 30mm are referred to as lung masses, and lung nodules with a diameter of 12mm are classified as medium-sized lung nodules. For lung nodules of 8~30mm, regular follow-up is required as prescribed by the doctor. By perfecting chest CT and other examinations, changes in the size, morphology and traits of the nodules can be observed, which will help to assess the benignness or malignancy of the nodules. It is recommended that patients with 12mm lung nodules should seek timely medical treatment, adjust their mindset during the treatment period, look at the disease correctly, and undergo examination and treatment as early as possible. At the same time, you should quit smoking and alcohol, do not eat cold and spicy stimulating food.