A wide variety of cystic and mass-like lesions can occur in the chest of infants and children, but those that cause acute symptoms are often associated with pneumonia or infection of pre-existing congenital or developmental lung lesions. Pediatric chest masses can be classified by location, multiplicity, and the presence or absence of air-filled or fluid-filled cysts. Characteristic radiographic findings are diagnostic for some lesions, whereas others can appear quite similar radiographically. This article illustrates the common chest masses and cysts that present emergently in pediatric patients and discusses imaging approaches to the diagnosis of such lesions.