Radiotherapy is an important treatment modality for non–small cell lung cancer (NSCLC). There are models of radiotherapy utilization that estimate the proportion of patients with NSCLC who have an evidence-based indication for radiotherapy. These estimates range from 46%-68% for radiotherapy utilization at diagnosis and 64%-75% overall. However, actual radiotherapy utilization throughout much of the world is lower than this, ranging from 28%-53%, with the largest differences between actual and estimated radiotherapy utilization seen in stage III NSCLC. Some of this discrepancy is attributable to the assumptions in the models that are based on broad factors such as stage and performance status. Characteristics of the population with underlying lung cancer that often has comorbidities or compromised respiratory function also influence the ability to deliver radiotherapy safely. Sociodemographic factors such as race and income have been found to affect access to radiotherapy in certain jurisdictions. The type of clinician or medical setting the patient presents to initially can also influence radiotherapy use in NSCLC. Potential solutions to improve appropriate radiotherapy utilization for NSCLC include restructuring models of care to ensure that all patients with lung cancer are managed within a multidisciplinary team including a radiation oncologist.