Computed tomography(CT) is indispensable for diagnostic imaging. During preoperative assessment for cardioaortic surgery, a CT examination is performed not only for diagnostic purposes but also to decide the surgical strategy. In some cases, CT demonstrates a small abnormal mass in the adipose tissue of the anterior mediastinum. Sometimes radiologists diagnose the image and send the diagnostic report to cardiologists or cardiovascular surgeons. However, they tend to limit their focus to their field of specialty. Thus, they might overlook or underestimate an abnormal mass. Anterior mediastinal masses, though small, may include malignant tumors. Thus, we reviewed 12 cases in which anterior mediastinal masses were found on preoperative CT. Two of these patients were finally diagnosed with malignant tumors. We should pay attention to not only cardiovascular assessment but also mediastinal masses on preoperative CT. In some cases, concomitant surgery for cardioaortic disease and an anterior mediastinal tumor is effective.