Recent evidence demonstrates the importance of microRNAs (miRNAs) in several human diseases, including solid and hematological malignancies, diabetes and diseases of the nervous system. However, little is known about the role that miRNAs play in the development and pathogenesis of lung diseases. Murine models of disease suggest that the loss of specific miRNAs is vital to lung development and modulation of the immune system that consequently results in the development of uncontrolled inflammation in the lung. Other studies have found that bacterial challenges also upregulate the expression of specific miRNAs. In this article, we will focus on miRNA involvement in lung development and the possibility that dysregulation and/or reactivation of miRNAs may contribute to lung disease. We will also review the role of miRNAs in the pathogenesis of specific diseases, such as lung cancer, sepsis and smoking-related lung disease.