Objective: Asthma is the most common chronic lung disease in childhood. Difficult-to-treat asthma is defined as the continuation of symptoms or attacks of patients despite step 4 or 5 of Global Initiative for Asthma therapy. In the differential diagnosis of these patients, flexible fiberoptic bronchoscopy is recommended to exclude other lung diseases. In this study, we aimed to examine the clinical and radiologic features and flexible fiberoptic bronchoscopy findings of patients referred to our pediatric pulmonology department due to difficult-to-treat asthma and determine the effects of flexible fiberoptic bronchoscopy on the differential diagnosis and treatment. Materials and Methods: The demographic characteristics and flexible fiberoptic bronchoscopy results of 62 patients who were diagnosed as having difficult-to-treat asthma in our pediatric pulmonology department between January 2015 and June 2020 were evaluated retrospectively. The symptoms, history, medications, physical examination findings, pulmonary function tests, and radiologic findings of patients who underwent flexible fiberoptic bronchoscopy were evaluated. Results: The median age of the patients was 69 (interquartile range: 42-108 months). The most common reasons for the referral of these patients were chronic cough, recurrent pulmonary infections, and persistent wheezing. All patients had chest radiography and 37 (59.7%) had chest computed tomography at their first admission; 14 (37.8%) patients had abnormal findings on chest computed tomography. There was no significant difference in terms of age, physical examination findings, pulmonary function test results, and radiologic examinations between patients with and without pathologic bronchoscopy findings. None of the patients had complications during and after flexible fiberoptic bronchoscopy. The most common diagnoses of patients based on flexible fiberoptic bronchoscopy were persistent bacterial bronchitis in 19 (30.6%) patients, tracheomalacia and/or bronchomalacia in 12 (19.4%), and anatomic anomalies in 3 (4.8%) patients (separation of lingula into 3, separation of right upper lobe bronchus into 4, and tracheal dyskinesia). Mycobacterium tuberculosis growth was observed in the tuberculosis culture of 1 patient. According to the flexible fiberoptic bronchoscopy and bronchoalveolar lavage results, antituberculosis treatment was initiated in 1 patient and polypoid mass excision was performed in 1 patient. A proton pump inhibitor was started in 9 (15.5%) patients, physiotherapy in 5 (8.0%), antibiotics in 14 (22.5%), and ipratropium bromide in 7 (11.2%) patients. All patients were followed up with the diagnosis of asthma except for 2 patients. Conclusion: To date, there is no prospective study evaluating the importance of flexible fiberoptic bronchoscopy in difficult-to-treat asthma in childhood. In our small cohort, persistent bacterial bronchitis, airway tracheomalacia and/or bronchomalacia, gastroesophageal reflux, and other anatomic anomalies were successfully diagnosed using flexible fiberoptic bronchoscopy and treated without any complications, suggesting that flexible fiberoptic bronchoscopy is an important diagnostic tool with a low complication rate in children with difficult-to-treat asthma. Cite this article as: Büyükşahin HN, Emiralioğlu N, Tural DA, et al. The importance of flexible bronchoscopy in difficult-to-treat asthma from a pediatric pulmonology perspective. Turk Arch Pediatr. 2022;57(3):310-315.