Recently, the classification of diffuse parenchymal lung diseases was revised. Based on histologic criteria, six different syndromes of idiopathic interstitial pneumonias were defined in this new system. Several studies have shown that this classification is indeed of clinical relevance. Furthermore, immunological studies have revealed different pathomechanisms for the distinct diseases. Different treatment strategies have been developed for each class of idiopathic interstitial pneumonia. While in T-cell dependent disorders the benefit of immunosuppressive treatment has been described, in disorders with predominately fibrotic remodeling new treatment options are urgently needed, and only lung transplantation has been shown to improve mortality.