© 2014 Aryal et al. Chronic obstructive pulmonary disease (COPD), one of the most common chronic diseases and a leading cause of death, has historically been considered a disease of men. However, there has been a rapid increase in the prevalence, morbidity, and mortality of COPD in women over the last two decades. This has largely been attributed to historical increases in tobacco consumption among women. But the influence of sex on COPD is complex and involves several other factors, including differential susceptibility to the effects of tobacco, anatomic, hormonal, and behavioral differences, and differential response to therapy. Interestingly, nonsmokers with COPD are more likely to be women. In addition, women with COPD are more likely to have a chronic bronchitis phenotype, suffer from less cardiovascular comorbidity, have more concomitant depression and osteoporosis, and have a better outcome with acute exacerbations. Women historically have had lower mortality with COPD, but this is changing as well. There are also differences in how men and women respond to different therapies. Despite the changing face of COPD, care providers continue to harbor a sex bias, leading to underdiagnosis and delayed diagnosis of COPD in women. In this review, we present the current knowledge on the influence of sex on COPD risk factors, epidemiology, diagnosis, comorbidities, treatment, and outcomes, and how this knowledge may be applied to improve clinical practices and advance research.