Congenital diaphragmatic hernia (CDH) is a congenital malformation of the diaphragm that allows the abdominal organs to push into the chest cavity. We report the case of a 15-month-old patient who presented with a non-resolving opacity on a chest radiograph despite extensive antibiotic treatment. A large anterior mediastinal mass was seen on the chest radiograph with effacement of the right cardiac border and accompanying diminution of the liver shadow, suggesting intrathoracic herniation of abdominal contents. A computed tomography (CT) scan confirmed the presence of abdominal contents in the right hemithorax. Congenital diaphragmatic hernias can cause uncertainty in diagnosis and difficulty in subsequent treatment. Non-resolving chest opacities warrant further investigation by cross-sectional imaging such as a CT scan.