SUMMARY Congenital diaphragmatic hernias are often symptomatic in the neonatal period. However, up to 5% of the patients can remain asymptomatic until later in life and the appropiate diagnosis is challenging for pediatricians in these cases. We present an 11-month old male with a mass located in the left hemithorax. The patient did not have previous respiratory symptoms related to the diaphragmatic hernia. A chest CAT scan confirmed a left diaphragmatic hernia and the subsequent surgical correction was uneventfull.