Interstitial lung diseases are a group of diffuse parenchymal lung disorders associated with substantial morbidity and mortality. Knowledge achieved in recent years has resulted in the publication of the new classification of idiopathic interstitial pneumonias, according to which there are three groups: major, rare and unclassified. The novelty of the new classification comes from the fact that difficult to classify entities can be treated according to the disease behaviour classification. Idiopathic pulmonary fibrosis is the most lethal amongst the interstitial lung diseases and presents high heterogeneity in clinical behaviour. A number of biomarkers have been proposed in order to predict the course of the disease and group patients with the same characteristics in clinical trials. Early diagnosis and disease stratification is also important in the field of other interstitial lung diseases.