Cognitive dysfunction is very common in chronic obstructive pulmonary disease (COPD) patients, but the mechanism has not been illustrated clearly. The common thought internationally is that chronic hypoxia and/or hypercarbia play important roles in the process of neuron damage. Hypoxia activates body′s inflammatory response and releases a series inflammatory factors that contribute to the endothelial dysfunction and neuron damage. Recent years, many reports pointed out that the chronic hypoxia is a high risk factor in the progress of Alzheimer′s disease. The current studies of the relation between COPD with cognitive dysfunction and dementia of Alzheimer′s disease are reviewed in this article.