The co-existence of presence of systemic inflammation in COPD and of several comorbidities is the most popular research area recently in pulmonology. Although it is a controversial issue, the presence of low-grade ongoing systemic inflammation in COPD is an accepted conception. However, in a recent study, systemic inflammation has revealed in a small group of COPD patients. The presence of oxidative stress has been accused of developing of COPD by inflammatory cells, as a part of systemic inflammation, and cigarette smoke. By exploring the role of oxidative stress, with various complex mechanisms, in the pathogenesis of COPD, will provide new therapeutic options in the treatment of COPD.