Shadows in the lungs are not equal to lung cancer and further examination should be done. Common diseases with shadows in the lungs: pneumonia, tuberculosis, benign lung tumors, pulmonary fungal disease, silicosis, pulmonary fibrosis, COPD, and lung cancer (peripheral type lung cancer). For early detection of lung cancer, regular checkups are required. In addition to the routine chest X-ray, regular checkups include tests specifically designed to diagnose lung cancer. The purpose of this is to screen for “people who may have abnormalities in their lungs. When we see a lung shadow on an X-ray, it does not mean that “it is lung cancer”. However, it should be taken as a sign of an abnormality and alert the patient to the need for a more detailed examination. In addition, there are also people who have lung cancer when their x-rays look normal. Therefore, for early detection of lung cancer, sputum for cancer cells and spiral CT chest examination are recommended.