Dendritic cells (DCs) are potent antigen-presenting cells. Because of their particular ability to initiate and regulate cell mediated and humoral immune responses, there is considerable interest in the role that DCs play in the pathogenesis of various lung diseases, especially those in which there is an excessive immune response to specific antigens (as in asthma) or a deficient immune response (as in lung cancer). A number of DC subpopulations have been defined in the lungs, including myeloid or conventional DCs that initiate T-cell immunity and antibody production and plasmacytoid DCs that have an important role in antiviral immunity and immune tolerance. Although an extensive body of literature has documented the role that DCs play in experimental models of lung disease, this review will highlight recent advances in our understanding of DC function in human disease, including asthma, COPD, antimicrobial immunity, and lung cancer. The future is likely to see new approaches whereby antigens and small molecules are targeted to receptors on particular DC subpopulations in order to modify pulmonary immune responses.