The staging of non-small lung cancer has to be performed in an interdisciplinary approach considering all clinical, radiological and histologic results. The staging using imaging procedures is done according to the TNM classification with T describing the extent of the primary tumor, N the presence and location of metastatic lymph nodes and M the presence or absence of distant metastases. It is important to remember that the individual stages of the TNM classification have undergone numerous revisions and thus need to be considered in their most recent version [Chest 111 (1997) 1718; Chest 111 (1997) 1710]. Noninvasive information about the stage of the disease is important for the planning and optimization of therapy. This may be done with imaging procedures such as, CT, MRT or PET.