Extracellular ATP is up-regulated in the airways of patients with chronic obstructive pulmonary disease, and may contribute to the pathogenesis of the disease. However, the precise mechanisms are poorly understood. Our objective was to investigate the functional role of the ATP receptor P2X(7) in the pathogenesis of cigarette smoke (CS)-induced lung inflammation and emphysema in vivo. Expression of the P2X(7) receptor (P2X(7)R) was measured in lung tissue und immune cells of mice with CS-induced lung inflammation. In a series of experiments using P2X(7) antagonists and genetically engineered mice, the functional role of the P2X(7)R in CS-induced lung inflammation was explored. CS-induced inflammation was associated with an up-regulation of the P2X(7)R on blood and airway neutrophils, alveolar macrophages, and in whole lung tissue. Selective intrapulmonary inhibition of the P2X(7)R reduced CS-induced lung inflammation and prevented the development of emphysema. Accordingly, P2X(7)R knockout mice showed a reduced pulmonary inflammation after acute CS exposure. Experiments with P2X(7)R chimera animals revealed that immune cell P2X(7)R expression plays an important role in CS-induced lung inflammation and emphysema. Extracellular ATP contributes to the development of CS-induced lung inflammation and emphysema via activation of the P2X(7)R. Inhibition of this receptor may be a new therapeutic target for the treatment of chronic obstructive pulmonary disease.