Airways disease is a hallmark finding in both asthma and chronic obstructive pulmonary disease (COPD). Although tobacco cigarette smoking is the largest known cause of COPD, recent studies have revealed that 10% of patients with life-long asthma may develop COPD later in life without ever smoking. The mechanisms underlying asthma transition to COPD are unknown. To better understand this transition, this proposal will use 129Xe magnetic resonance imaging (MRI), computed tomography (CT) imaging and oscillometry to measure airway abnormalities in patients with asthma, COPD, and asthma-COPD overlap. These measurements will provide a better understanding of airway abnormalities that contribute to development of COPD in these patients with asthma. COPD is the most common cause of hospital admission in Canada and treatment costs in BC alone are estimated to be over $600M/year. The results generated from this proposal may identify new ways to treat COPD or halt its development in patient with asthma, contributing to reduced hospital admissions and costs related to COPD.