In the diagnosis of lung cancer, tissue and cytologic specimens are needed for confirmation of the diagnosis, elucidation of the histologic type of lung cancer, determination of the extent of the cancer, and increasingly also for the molecular biological investigations required for the planning of drug therapy. The site and method of specimen collection are chosen multidisciplinarily on the basis of imaging studies, taking the clinical picture and patient safety into consideration. High-quality and quantitatively representative specimens are required for molecular biological analyses, and assessment of the response to drug therapy or modifying the treatment may require a new sample, which can be a tissue or cytologic specimen or a liquid biopsy.