BACKGROUND: When gastro-oesophageal reflux is causing symptoms or lesions in the oesophagus, this is referred to as gastro-oesophageal reflux disease (GERD). GERD can manifest itself through typical symptoms (heartburn, regurgitation) or may lead to extra-oesophageal symptoms. Extra-oesophageal manifestations of GERD gained increasing attention over the last decade, especially respiratory disorders, because of the prevalent co-occurrence with GERD. The role of GERD in the pathogenesis of respiratory disorders has become a topic of intense discussion. AIM: To provide an overview of the current knowledge on the role of GERD in asthma and chronic obstructive pulmonary disease (COPD). METHODS: PubMed was searched for relevant articles using the keywords: GERD, asthma, COPD, prevalence, treatment. Case reports were excluded, only English language articles were considered. RESULTS: Estimates for the prevalence of GERD in asthma range from 30% to 90%, compared to an average of 24% in controls. In COPD patients, the prevalence of GERD ranges from 19% to 78% compared to an average of 18% in controls. These data indicate an increased prevalence of GERD in patients with asthma and COPD, although causality is not established and GERD treatment yielded inconsistent effects. Literature supports GERD as a risk factor for COPD-exacerbations and a predictor of the 'frequent-exacerbator'-phenotype. CONCLUSIONS: Despite the high prevalence of GERD in asthma and COPD, a causal link is lacking. The results of anti-reflux therapy on pulmonary outcome are inconsistent and contradictory. Future studies will need to identify subgroups of asthmatics and COPD patients that may benefit from anti-reflux therapy (nocturnal or silent reflux).