Cystic fibrosis (CF)-related lung disease is characterized by a broad spectrum of pathologic changes. Most of these changes relate to progressive bronchiectasis and airway destruction due to recurrent infections. Other airway pathologies include but are not limited to nasal polyposis, bronchial hyperactivity, pneumothorax and allergic bronchopulmonary aspergillosis (ABPA). Constrictive obliterative bronchiolitis (COB) in CF is usually seen in post-transplant settings including lung and heart-lung transplants. We report a 13-year-old boy with CF and intractable deterioration in lung function that was ultimately diagnosed as COB.