Magnetic resonance imaging of the trachea was performed in 21 children with congenital or acquired narrowing of the trachea or main bronchi. Diagnosis included aortic arch anomalies, innominate artery compression, pulmonary artery compression and tracheomalacia. All patients were examined after bronchoscopy. The demonstration of the trachea and the surrounding tissue and vessels on MR images enables the cause of tracheal compression and the degree and location of collapse to be evaluated. MRI is a modality well suited to characterizing tracheal narrowing without employing ionizing radiation or intravenous contrast medium. All MRI examinations were carried out with the patient under general anaesthesia so as not to risk pulmonary deterioration during sedation. In the cases presented MRI is the diagnostic step of choice after tracheobronchoscopy and broadens the diagnostic potential in extrinsic tracheal or bronchial stenosis in paediatric patients.