Vascular rings are congenital defects of great vessels. They cause compression of the trachea or/and the esophagus and therefore result in symptoms like inspiratory stridor, cough, wheezing, recurrent respiratory tract infections or dysphagia. In some cases, the correct diagnosis can be delayed for many years, especially when vascular rings produce less severe symptoms or symptoms mimicking other diseases (most of all asthma). In this article, we would like to emphasis the usefulness of pulmonary function test (spirometry) in the initial diagnosis of vascular rings in school-aged children, as well as the importance of spirometry in evaluating patients with asthma presumption.