Acquired tracheobronchomalacia (TBM) is an uncommon complication of severe lung disease in infancy. We report a case of TBM in an ex-premature infant with severe chronic lung disease (CLD). Multidetector computed tomography (MDCT) was used to dynamically assess the patency of the large airways at different time periods during the infant's hospital course. Initially at 3 months of age, the airways maintained patency during both phases of the respiratory cycle, but at 6 months of age, diffuse TBM was evident on MDCT. Appropriate management with long-term positive end expiratory pressure (PEEP) was initiated for the infant once the diagnosis of acquired TBM was confirmed. The case highlights the efficacy and relative ease of early diagnosis of acquired TBM by MDCT in infants at risk of this condition.