Purpose : In Korea, Lung cancer is the Second most common prevailing malignancy among male population next to stomach cancer. Although CT scan and MRI is widely used in the staging of lung cancer, plain chest x-ray still plays an important role in screening and diagnosis. Our intention was to review the confusing radiographic features which result in delayed diagnosis of lung cancer.Materials and Methods: Of the 160 patients with lung cancer evaluated by us, 62 patients(39%) with delayed diagnosis had average diagnostic duration of 5.1 months compared with 2.1 months for those without delay. We reviewed the plain chest x-ray findings of those 62 patients.Results : The diagnosis of lung cancer was delayed more than half of the cases under the impression of intrathoracic tuberculosis. Upon reviewing the roentgenologic findings in patients with diagnostic delay, central type appeared as a small hilar or mediastinal mass with or without obstructive pneumonia. Peripheral type appeared as an ill-defined pulmonary nodule, a nodule hidden by overlapping structures, or as a lung cancer associated with pulmonary tuberculosis. Some cases were misinterpreted as extranodal spread of malignancy.Conclusion : To solve above mentioned problems, we recommend proper understanding of natural history of lung cancer, incorporation of high kVp technique in chest radiographs, routine acquisition of lateral chest radio-graph to increase diagnostic accuracy, and appropriate use of CT scan In cases of difficult diagnosis.