Lung cancer is usually suspected in individuals who have abnormal chest radiograph findings or have symptoms caused by either local or systemic effects of the tumor. The method of diagnosis of suspected lung cancer depends on the type of lung cancer (ie, small cell lung cancer or non-small cell lung cancer), the size and location of the primary tumor, the presence of metastasis, and the overall clinical status of the patient. Achieving a diagnosis and staging are usually done in concert because the most efficient way to make a diagnosis often is dictated by the stage of the cancer. The best sequence of studies and interventions in a particular patient involves careful judgment of the probable reliability of a number of presumptive diagnostic issues, so as to maximize the sensitivity and to avoid performing multiple or unnecessary invasive procedures. In this article, we consider all manner of clinical presentations of lung cancer in light of currently available diagnostic procedures. Published data supporting a particular diagnostic approach is weighed based on the quality of the benefit as well as the estimated net benefit. Recommendations are graded in terms of strength to provide clinicians with guidance as to the most efficient and approach to the diagnosis of lung cancer in individual patients.