The main difference between a chest X-ray and a CT is that the CT image is clearer and can show smaller lesions. If a patient has a mass on the lung, it can be detected on a chest X-ray if the lesion is large. However, if it is a small nodule or glassy nodule, the chest X-ray has its limitations and the image is not clear, so the lesion may be missed and not detected. However, CT is able to show smaller lesions and subtle structural changes within the lesion, which can provide more information to the diagnosing physician to diagnose whether the lesion tends to be malignant or benign. Therefore, CT shows the structures more clearly and can also show the presence of enlarged lymph nodes in the mediastinum.