we further attempted to find morphological evidence that accounts for cognitive impairment in COPD patients. Therefore, we measured hippocampal volume in patients with different severity of COPD. Surprisingly, we found that hippocampal atrophy did occur in COPD patients and there were significant correlations with PaO2, SaO2 and MMSE which may account for cognitive decline in COPD patients. However, the mechanism is poorly understood. One possible explanation is that COPD patients exist in a state of low-grade systemic inflammation [3] and persistent airflow limitation which leads to chronic hypoxemia.