Giant cell arteritis (GCA) is a granulomatous vasculitis. Early diagnosis is important for the initiation of corticosteroid treatment because the arteritis can result in blindness. In most of the cases, the superficial cranial arteries are affected. However, extracranial involvement of various arteries is known. Here, we report a case of histologically proven GCA with an inflammatory stenosis of the right vertebral artery. For complete evaluation of the extension of the disease, an optimized protocol of high-resolution magnetic resonance imaging at 3 T in combination with contrast-enhanced magnetic resonance angiography was performed. This non-invasive method facilitates the differentiation of inflamed and healthy segments of small cranial arteries, may help to find appropriate sites for biopsy, and allows the assessment of affected extracranial vessels. In this patient case, even the cause of vertebral stenosis--inflammatory versus arteriosclerotic--could be elucidated.