Primary cardiac tumors are quite rare and most of these tumors are benign. In this report, a patient presented with chest distress and shortness of breath after activity. Echocardiography of other hospital showed a hyperechoic right atrial mass. Electrocerdiogram-gated cardiac computed tomography (ECG-Gated CT) of our hospital provided accurate information about the site and extent of the tumor, and the involvement of neighboring structures, even about the malignant nature of the lesion. The pathological study indicated angiosarcoa. The role of ECG-Gated CT in the assessment of cardiac masses and tumors was discussed. Cardiac tumors are extremely rare and can be divided into benign and malignant lesions. Myxomas are the most common type of cardiac benign tumor, while angiosarcomas are the most common type of cardiac malignant tumor.Imaging studies play an important role in the diagnosis of cardiac angiosarcomas. Echocardiogram, computed tomography (CT) and magnetic resonance imaging (MRI) are the most common imaging studies for tumors evaluation. However, the precise tumor location is often difficult to evaluate precisely on the basis of two-dimensional source images. We conducted ECG-gated cardiac CT examination with 3D reconstruction for preoperative assessment in a patient with a angiosarcoa arising in the right atrium.