Differential diagnosis of uncertain swelling of the neck has a limited number of possibilities. Thyreoideal processes, lymphatic adenomatosis and abscesses are in most of these cases prevent. However, vascular diseases should be also considered. It is current practice to perform a sonography, completed by computertomography for establishing a diagnosis. If vascular disease is suspected also an angiography is indicated. During the diagnostic procedure we discovered a major aneurysm of the left external carotid artery. The aneurysm was resected and vascular continuity restored by PTFE patchplasty. In case of tumorous processes of the neck extracranial aneurysms of the carotid artery have to be included into the differential diagnosis in order to guarantee adequate therapy.