The registries can provide an alternative and important source of clinical data, significantly contribute to better understanding of pulmonary diseases and outline requirements for their effective management. Moreover, the registries can support both regulatory and routine clinical decision-making. Randomized controlled trials (RCTs) are essential for the approval of new therapies; however, because of their design, they provide little insight concerning disease epidemiology/etiology and current clinical practice. Particularly, in lung disease, rigid inclusion/exclusion criteria can limit the generalizability of pivotal trial data. Noninterventional studies (NIS), conducted through the well-established mechanism of patient registries, are undervalued as a means to close data gaps left by RCTs by providing essential data that can guide patient care at different levels from clinical decision-making to health-care policy. In particular in rare diseases their importance cannot be underestimated. In respiratory disease, registries have been essential in understanding the natural history and different phenotypes of rare conditions, such as alpha 1 antitrypsin deficiency, cystic fibrosis, and idiopathic pulmonary fibrosis. Importantly, additional therapeutic outcome data were generated. While measures for enhancing data quality in RCTs have evolved significantly, the approach and effectiveness of registries is variable. Specific limitations of registry data should be recognized as well as challenges to registry operation, including the impact of the European Union General Data Protection Regulation. Therefore, RCTs and registry studies should be viewed in parallel, with both providing distinct but complementary data.