Non-small cell lung cancer is a common disease. Adeno- and squamous-cell type are the most frequent subtypes, the former with rising incidence. The clinical picture is nonspecific until late in the course of the disease. The most important diagnostic tools are chest X-ray, computed tomogram of the chest, and bronchoscopy. Additional tests often used for staging are abdominal ultrasound, computed tomography of the abdomen, bone scintigraphy, and magnetic resonance imaging of the head. Positron emission tomography is of rising importance. Therapy is guided by stage. Stage I disease is a domain of surgery, in stage II combined with adjuvant chemotherapy. In stage III, multimodality treatment, mostly chemoradiotherapy, is indicated. Stage IV disease is treated with palliative chemotherapy. Newer, so-called targeted therapies are more and more implemented into therapy. There are three substances approved for second-line therapy with response rates of just under 10%.