Chronic obstructive pulmonary disease (COPD) is defined as persistent airflow limitation by spirometry. However, some smokers with normal spriometry have significant respiratory symptoms. We used 3He apparent diffusion coefficient (ADC) to examine the lungs in older smokers with and without COPD (n=50). This study showed high ADC in both smokers with and without COPD. The difference in ADC between COPD and non-COPD was significant. ADC was correlated positively with percent emphysema and %FVC, and negatively with FEV1 to FVC ratio and, non-significantly with FEV1. 3He ADC may provide different information of lung microarchitecture from spirometry in smoking related pulmonary diseases.