Even the most sophisticated examinations, such as computerized tomography and percutaneous fine needle biopsy, often do not allow a certain preoperative diagnosis of benign lung cancer. The clinical history may also be deceiving: a smoker over 35 years of age need not necessarily have a primary lung cancer, but this event is frequent enough to justify a diagnostic thoracotomy. In our series, chest tomography proved to be useful and sometimes revealed unsuspected lesions. In contrast, bronchoscopy is useful only for centrally located lesions, and the same is true for bronchial washing and brushing. Finally, thoracotomy, possibly an axillary one with enucleation or possibly transegmentary resection, is the most frequent operation in benign lung tumors, because of the unfailing diagnosis and for the minimal functional damage to the patient. A diagnostic thoracotomy may also avoid the psychologic stress suffered by a patient with a simple but undiagnosed benign lung tumor.