Background: Dysfunctional breathing (DB) has been shown to negatively affect asthma control in adults, but for children and adolescents, the knowledge is scarce.DB is among others characterized by dyspnea and hyperventilation. The Nijmegen Questionnaire (NQ) is often used as a marker for DB. We conducted a cross-sectional survey to estimate the prevalence of DB in patients with asthma in a pediatric outpatient clinic and to determine the impact of DB on asthma control.Methods: Patients between 10 and 17 years were invited to complete the NQ and the Asthma Control Questionnaire (ACQ) and report the use of beta2 agonist (β2).Spirometry data and prescribed asthma medications were noted from the patient record.Results: Three hundred and sixty-three patients (180 boys) completed the survey.Sixty-seven patients (18%) scored ≥23 points in the NQ predicting DB. The DB group was older (median (range)) 15.