A 43-year-old man with no history of cardiac disease was referred to our hospital for the study of an episode of a haemodynamically unstable regular monomorphic wide QRS complex tachycardia. The cardiac magnetic resonance imaging (MRI) showed the presence of sub-epicardial fibrosis in the mid-anterolateral segment of the left ventricle. Scar dependent ventricular tachycardia (VT), even in the absence of cardiac disease, and idiopathic VT are different conditions. Delayed gadolinium MRI could be useful in the differential diagnosis between them.