Different techniques to predict postoperative lung function have been reported but there has not been a quantitative review of their accuracy and precision. Predictions are used to inform important treatment decisions such as whether to proceed with surgical resection or recommend other treatment modalities (such as radiotherapy or chemotherapy). Predictions are a factor in counselling patients about their operative risk and a national audit reported that patient preference is a significant reason that patients with resectable tumours do not undergo resection . In addition, prediction resulting in high-risk assessment may delay treatment to allow time for further investigations, such as cardiopulmonary exercise testing. Thus, there is a need for formal comparison of prediction methods.