Patients with lung cancer face concurrent risks of their disease by local, regional as well as distant failure. The brain is one of the major sites of distant relapse and the prevention of cerebral metastasis has therefore gained rising interest. A recent meta-analysis has confirmed the benefit of prophylactic cranial irradiation in patients with limited disease small-cell lung cancer in complete remission following induction therapy. In non-small-cell lung cancer, aggressive multimodality therapy regimens including surgery have achieved locoregional control rates of 50% and higher. In these patient groups the relatively high incidence of brain relapses as a site of first failure causes substantial morbidity and worsens the prognosis. Given the proven efficacy of prophylactic cranial irradiation (PCI) to prevent metastases to the brain, the introduction of PCI into the treatment of non-small cell lung cancer in the curative setting seems promising.