Croup (laryngotracheitis) is a common diagnosis made in children six months to three years of age. Characteristic symptoms include a inspiratory stridor, barking cough, and hoarseness. The most common etiology is parainfluenza virus
These images are from Dr. Paula Brill's excellent pediatric radiology collection.
Dr. Brill is a professor in the department of radiology (pediatric section) at Weill Cornell.