BackgroundDyspnoea is a common persistent symptom after COVID-19. Whether it is associated with functional respiratory disorders remains unclear.MethodsWe assessed the proportion and characteristics of patients with “functional respiratory complaints” (FRCs) (as defined by Nijmegen Questionnaire>22) among 177 post-COVID-19 individuals who benefited from outclinic evaluation in the COMEBAC study (i.e., symptomatic and/or ICU survivors at 4 months). In a distinct explanatory cohort of 21 consecutive individuals with unexplained post-COVID-19 dyspnoea after routine tests, we also analysed the physiological responses to incremental cardio-pulmonary exercise testing (CPET).FindingsIn the COMEBAC cohort, 37 had significant FRCs (20.9%, IC95: 14.9–26.9). The prevalence of FRCs ranged from 7.2% (ICU patients) to 37.5% (non-ICU patients). The presence of FRCs was significantly associated with more severe dyspnoea, lower 6-minute walk distance, more frequent psychological and neurological symptoms (cognitive complaint, anxiety, depression, insomnia and post-traumatic stress disorders) and poorer quality of life (all p<0.01). In the explanatory cohort, 7/21 patients had significant FRCs. Based on CPET, dysfunctional breathing was identified in 12/21 patients, 5/21 had normal CPET, 3/21 had deconditioning and 1/21 had evidence of uncontrolled cardiovascular disease.InterpretationFRCs are common during post-COVID-19 follow-up, especially among patients with unexplained dyspnoea. Diagnosis of dysfunctional breathing should be considered in those cases.FundingAssistance Publique-Hôpitaux de Paris.