Enlargement of the left hilar suggests changes such as chronic inflammation, enlarged lymph nodes or early tumors near the left hilar. Further differential diagnosis is needed if the patient develops enlarged left hilar after long-term smoking or exposure to dust, cough, sputum, blood in sputum, chest pain, and progressive wasting. If tuberculosis is considered, a T-cell test for tuberculosis infection and a fiberoptic bronchoscopic biopsy for the formation of microscopic neoplastic organisms need to be given. If the left hilar enlargement is caused by early stage lung cancer, enhanced CT of the chest should be given. If necessary, fiberoptic bronchoscopy, combined with biochemical examination and tumor marker measurement, should be given to understand the possibility of early-stage lung cancer. In conclusion, the enlargement of the left hilar lung should be considered to be caused by chronic inflammation, tuberculosis or lung cancer, and enhanced CT chest examination and fiberoptic bronchoscopic biopsy can be performed to assist in the diagnosis and to avoid any missed diagnosis or misdiagnosis.