We report the case of a 17-year-old boy with cystic fibrosis (CF) who presented with persistent cough; after starting intravenous antibiotics for Pseudomonas aeruginosa he underwent a computed tomography (CT) scan of the chest. CT revealed extensive consolidation in the right lower lobe with relative bronchus obstruction; the cause of bronchial obstruction was detected in the mediastinal window, corresponding to a bronchial tree-shaped, thick, tenacious mucous plug. This was extracted 48 h after unresponsive bronchial washing and endobronchial instillation of rhDNAse, using foreign-body forceps, with subsequent resolution of cough. This case, which is the second report of plastic bronchitis in CF, was resolved by mechanical removal of the mucous plug, suggesting that a careful observation of CT imaging may guide intervention aimed at resolution of atelectasis.