The QT interval in patients with catecholaminergic polymorphic ventricular tachycardia (CPVT) is typically normal. However, CPVT patients are sometimes misdiagnosed as concealed long QT syndrome (LQTS), because patients with LQTS also manifest with syncope or sudden death following periods of exertion or extreme emotion. We report a CPVT patient with a pathogenic RyR2 mutation associated with a marked QT prolongation, which normalized after flecainide therapy.