Brain metastases occur in 20-40 % of lung cancer patients. The use of whole brain radiation therapy (WBRT) has been shown to ameliorate many neurological symptoms, facilitate corticosteroid reduction, enhance quality of life (QOL), and prolong survival. The acute and early delayed side effects of WBRT are generally mild and inconsequential, whereas late complications often are progressive, irreversible, and may have a profound effect on neurocognitive function and QOL. Nevertheless, WBRT remains the cornerstone for treatment of multiple brain metastases due to its efficacy and the paucity of other treatment options. In avoidance of WBRT and its potential toxicity, patients of good performance status and ≤3 metastases may be treated reasonably with focal therapy alone (surgery or radiosurgery) without a compromise in survival. In patients with multiple brain metastases and those undergoing prophylactic cranial irradiation (PCI), established methods to mitigate the late complications of WBRT include total dose observation, dose per fraction restrictions, and avoidance of concomitant chemotherapy. Current areas of active research that hold great potential for benefit include hippocampal-sparing radiotherapy and the use of neuroprotective agents.