IntroductionThe coexistence of COPD and bronchiectasis seems to be common and associated with a worse prognosis than for either disease individually. However, no definition of this association exists to guide researchers and clinicians.MethodsWe conducted a Delphi survey involving expert pulmonologists and radiologists from Europe, Turkey and Israel in order to define the “COPD– [bronchiectasis] BE association”.A panel of 16 experts from EMBARC selected 35 statements for the survey after reviewing scientific literature. Invited participants, selected on the basis of expertise, geographical and sex distribution, were asked to express agreement on the statements. Consensus was defined as a score of ≥6 points (scale 0 to 9) in ≥70% of answers across two scoring rounds.Results102 (72.3%) out of 141 invited experts participated in the first round. Their response rate in the second round was 81%. The final consensus definition of “COPD–BE association” was: “The coexistence of (1) specific radiological findings (abnormal bronchial dilatation, airways visible within 1 cm of pleura and/or lack of tapering sign in ≥1 pulmonary segment and in >1 lobe) with (2) an obstructive pattern on spirometry ([forced expiratory volume in 1 s] FEV₁/[forced vital capacity] FVC <0.7), (3) at least two characteristic symptoms (cough, expectoration, dyspnoea, fatigue, frequent infections) and (4) current or past exposure to smoke (≥10 pack-years) or other toxic agents (biomass, etc.)”. These criteria form the acronym “ROSE” (Radiology, Obstruction, Symptoms, Exposure).ConclusionsThe Delphi process formulated a European consensus definition of “COPD–BE association”. We hope this definition will have broad applicability across clinical practice and research in the future.