18F-FDG PET offers the radiation oncology community the ability to incorporate biologic information into radiation therapy targets. To date, most of the work in this arena has involved patients with non-small cell lung cancer (NSCLC). The literature suggests that biologic targeting with PET alters the radiation treatment volume significantly in 30%-60% of NSCLC patients for whom definitive therapy is planned. This is mostly the result of the incorporation of regional nodes with 18F-FDG avidity that were previously judged to be uninvolved by CT criteria. The development of the integrated PET/CT scanner is a valuable tool that improves diagnostic accuracy for staging this disease and will increase the accessibility of PET for radiation treatment planning. Its implementation into radiation treatment planning requires strong collaboration between radiation oncologists and nuclear physicians. In this report, we will review the literature on PET-based radiation treatment planning, its potential benefits, and future challenges.