Lung cancer is the leading cause of cancer-related mortality in the United States (US) and Canada. Because of the high incidence and mortality of this disease, small improvements in the management of this disease translates into large numbers of patients having improved outcomes after treatment. Radiation therapy is widely used to treat patients with lung cancer. However, the radiation dose to the tumor has been limited by the proximity of normal structures to the tumor, such as the lung, the spinal cord and the esophagus. The normal structures must not be exposed to excessive radiation doses. A new technique, called intensity-modulated radiotherapy delivers radiation to tumors such that the normal structures around the tumor are exposed to less radiation than previously achievable. This technique is already used to treat head and neck cancers. This study will use this technique to deliver more intensified radiation to the lung tumor after the patient receives two cycles of chemotherapy. A new imaging technique, called positron emission tomography (PET), has been found to be more sensitive and specific at detecting the extent of the tumor in the lung than the older imaging technique of computed tomography (CT). This study will use both the PET and CT to target the radiation beams. Following treatment, the patients will be followed up to assess the side effects of normal tissues and response of the tumor to the treatment.