Background: Dynamic flexible bronchoscopy (DFB) is considered as gold standard for the diagnosis of lower airway malacia (LAM) in child, but it is inadequately validated. Aims and Objectives: In this study, we aimed to evaluate the interobserver consistency in the diagnosis of LAM by DFB. Methods: We included children diagnosed with LAM by DFB (ERS 2019 report) or had normal bronchoscopic evaluation. Bronchoscopy evaluation was performed by a single operator, using the same device and three different sizes instruments. Videos were reviewed from archive by a paediatric pulmonologist who didn?t asses consistency. Videos were examined for the presence of LAM by six paediatric pulmonologists of various experience levels, without knowing clinical information. Consistency between observer one and others was compared with Cohen's kappa coefficient. Results: Videos of 100 children were included in this study. Seven, 59, and 36 bronchoscopies were performed using instruments with 2.8/3.8/4.8 mm diameters, respectively. The consistency comparison between observer one and others in terms of presence of LAM is given in Table 1. Interobserver consistency for the presence of malacia was better for large airways than for smaller. Conclusion: This is the first study evaluating interobserver consistency in the diagnosis of LAM with DFB video footage. Although there is generally moderate agreement among observers, it is lower, especially in relatively small airways. DFB used in the diagnosis of LAM in children is a method that gives instant and subjective data, and there is a need to develop an objective method or combine it with other diagnostic methods for definitive diagnosis.