Pericardial cysts are infrequent mediastinal entities. They can mimic cardiac chamber enlargement, phrenic hernia, malignancy, bronchogenic cysts, pleurisy, dextrocardia. Diaphragmatic elevation can also be misdiagnosed in some cases. The reports about huge pericardial cyst mimicking the left diaphragmatic elevation (paralysis) are not common. The correct diagnosis of pericardial cyst can be difficult due to unremarkable complains and non-specific findings on chest radiography. In this report we have presented a rare clinical case described as the huge pericardial cyst mimicking a false left diaphragmatic paralysis. The combination of different radiological technics (CT-scans, barium esophago-gastrography etc.) are useful to correct preoperative diagnosis. Transthoracic (intercostal) accesses are the dominant to operate on patients with huge pericardial cysts.