A 12-year-old boy with chronic respiratory complaints, including cough, exercise intolerance, and persistent wheezing, was referred to our hospital because of persistent symptoms under extensive asthma therapy. A standard radiograph of the chest detected very slight hyperinflation of the left lung with increased lung translucency (Figure 1). Computed tomography revealed a polypoid mass distally in the left main bronchus with a density around 55 HU and very slightly decreased attenuation of the left lung, probably due to secondary air trapping (Figure 2). Bronchoscopy confirmed this finding, and biopsy revealed the mass to be a low-grade mucoepidermoid carcinoma (Figure 3). A curative bronchial sleeve resection was performed with partial mediastinal lymphadenectomy. All lymph nodes were normal, and there is no recurrence to this date (one year). Adjuvant chemotherapy was not indicated.