Diffuse pulmonary nodular lesions have many causes. When they are caused by infection, the likely organisms are M. tuberculosis and various fungi. Silicosis, eosinophilic granuloma and pulmonary metastasis should be considered for differential diagnosis. Differential diagnosis needs detailed clinical history, physical examination and various laboratory tests. A case of persistent diffuse pulmonary nodular lesions which had persisted 5 years is reported. The patient was a 25 years old man with minimal pulmonary symptoms. Detailed past history and physical examination suggested thyroid tumor. Chest radiography showed numerous evenly sized well-defined nodules scattered in entire lung fields. Previous chest X-rays showed similar nodular lesions, which had lasted for 5 years. The number of nodules was slightly increased. Neck CT showed heterogenous mass in left lobe of thyroid gland and multiple lymphadenopathies along both internal jugular chains. Total thyroidectomy was performed. A case of lung metastasis which progressed slowly in papillary thyroid cancer is reported.