Aberrant Right Subclavian Artery (ARSA) is a rare vascular anomaly. It is though the most frequent anomaly involving the aortic arch, being present in about 1% of the general population. We present a case of a 71 year old male with symptoms of chronic cough and dysphagia. He was referred to our clinic for further evaluation of a mediastinal mass. A second Computed Tomography of the thorax was performed, this time with the use of i.v. contrast. The latter examination confirmed the diagnosis (ARSA), sparing the patient of invasive and potentially life threatening diagnostic procedures (invasive angiography, mediastinoscopy). This case highlights the significant pitfalls regarding the mediastinal evaluation, especially when i.v. contrast is not used. The majority of the mediastinal structures are vessels. Vessels abnormalities should be included in the differential diagnosis of a mediastinal mass.