BACKGROUND: Laryngomalacia is the most common congenital airway anomaly causing breathing difficulties in infants. Severe laryngomalacia is often associated with obstructive sleep apnea (OSA). METHODS: We re-evaluated 14-year pediatric sleep center polysomnography (PSG) data in infants with fluoroscopy-verified laryngomalacia. RESULTS: The study included 79 infants, with a median corrected age of 8 weeks (interquartile range, IQR 5-13) and a laryngomalacia clinical score of 10/14 (IQR 7-11). Most (78%) PSG studies were daytime studies. In PSG, laryngomalacia-related breathing difficulty appeared as a sleep stage and position-dependent OSA with laborious breathing. PSG allowed position comparison in 69 infants. In the supine sleeping position, a median obstructive apnea and hypopnea-index (OAHI) was 22 h CONCLUSIONS: In infant laryngomalacia, the degree of upper airway obstruction is frequently more severe in the supine than in the side sleeping position. However, some variability remains in the response. IMPACT: Laryngomalacia is the most common congenital airway anomaly causing breathing difficulties in infants. Obstructive breathing events and obstructive sleep apnea are common in severe laryngomalacia even though the stridor often diminishes or resolves during sleep. We observed that in young infants with laryngomalacia, the appearance of upper airway obstruction is both sleep position and sleep-stage dependent. Compared to the supine sleeping position, the side sleeping position reduced the frequency of obstructive events and breathing effort, and lowered end-tidal carbon dioxide 99th percentile levels.