Congenital absence of the pericardium is a rare cardiac condition, which can be either isolated or associated with other cardiac and extracardiac anomalies. There are six different types, depending on the severity of the involvement. Most of the patients with this defect are asymptomatic, especially the ones with complete absence of the pericardium. However, some patients are symptomatic, reporting symptoms that include chest pain, palpitations, dyspnea, and syncope. Diagnosis is established by the characteristic features on chest X-ray, echocardiogram, chest computed tomography (CT), and/or cardiac magnetic resonance imging (MRI). We present here a case of a 23 year-old-male, who presented to our hospital with complaints of pleuritic chest pain and exertional dyspnea, of a two-week duration. He was physically active and his past history was otherwise insignificant. His chest CT with contrast was interpreted as showing evidence of multiple emboli, predominantly in the left lung, and he was started on a heparin and warfarin therapy. A repeat chest CT with contrast three weeks later showed no significant change from the previous CT scan. Both scans showed that the heart was abnormally rotated to the left side of the chest. An echocardiogram raised the suspicion of congenital absence of the pericardium, with a posteriorly displaced heart. In retrospect, motion artifact on the left lung, attributed to cardiac pulsations and the lack of pericardium, resulted in a CT chest appearance, mimicking findings of pulmonary embolism. The misdiagnosis of pulmonary embolism was attributed to the artifact caused by excessive cardiac motion artifact on the chest CT scan. In non-gated CT angiograms, excessive motion causes an artifact that blurs the pulmonary vessels, reminiscent of a 'seagull' or a 'boomerang'. Physicians need to be aware of this phenomenon, as well as the characteristic radiological features of this congenital anomaly, to enable them to make a correct diagnosis.