In previous studies with hyperpolarised (HP) 3He MRI in smokers with normal pirometry and patients with early stage COPD, we showed sensitivity to early changes in lung ventilation and structure. The hyperpolarised gas MRI technique is safe. In particular, the lack of ionizing radiation permits patients to be imaged on multiple occasions. This and its inherent sensitivity to regional lung ventilation and function make it an ideal imaging tool for the assessment of novel lung therapies for diseases of the small airways.