Asthma and chronic obstructive pulmonary disease (COPD) affect the lives of a large portion of the population and can lead to morbidity and mortality. In many women, the incidence and severity of asthma exacerbations vary along their menstrual cycle. Estrogen, a natural occurring hormone, affects differently many of the cell types that are involved in asthma, including macrophages, eosinophils, neutrophils, lymphocyte, mast cells, fibroblasts, epithelial and smooth muscle cells. By binding to its receptors on the plasma or nuclear membrane, estrogen affects the expression of a plethora of proteins that are involved in the pathogenesis of asthma and COPD. In this review we will summarize the current knowledge of the role of estrogen in the expression, production and secretion of inflammatory agents that are involved in asthma and COPD and its potential therapeutic role in these diseases.