The techniques used for the investigation of a patient with lung carcinoma are determined by the mode of presentation of the disease. The first step is based on the clinical examination and the chest X-ray (frontal and lateral view). The pathological examination of the tumor represents the second step. Depending on the operability of the patient at this stage of the investigation, further evaluation will (or will not) be performed to determine the extension of the tumor, using TNM staging system. Any candidate for surgery has to be bronchoscoped in order to evaluate the endobronchial spread of the tumor and to look for additional lesions. Transverse tomography of the thorax is the central part of any staging procedure. The choice among the other methods of investigation depends on the site of the tumor in the thorax. Mediastinoscopy is only needed in case of a lesion of unknown nature located in the anterior mediastinum or in addition to CT scan when there is a suspicion of mediastinal involvement. Transthoracic needle aspiration is best performed on peripheral lesions. In small cell lung carcinoma, the preoperative work-up should be very systematic even in the absence of clinical or laboratory abnormality. Whereas in certain cases the investigation of a patient with lung carcinoma can be limited to a clinical examination and a chest X-ray, any candidate for surgery has to be submitted to a detailed TNM staging.