Stunned myocardium is often observed after unstable angina, myocardial infarction, thrombolysis, angioplasty, and bypass surgery but rarely after coronary vasospasm. A case of stunned myocardium caused by diffuse coronary artery vasospasm and mimicking myocardial infarction is reported. The patient had an emergency coronary angiography, which showed no pathological coronary disease, but the left ventricular ejection fraction showed severe left ventricular dysfunction. Repeat coronary angiography 24 days later after medical treatment (diltiazem and nitrates) showed complete recovery of wall function, and a diffuse vasospasm was induced in both coronary arteries (left anterior and right coronary arteries). Two days later the patient underwent a positron emission tomography study with water labelled with oxygen-15 to evaluate the viable myocardium and oxygen-15 to evaluate oxidative metabolism. The results showed normal myocardial blood flow and perfusable tissue density, confirming that the myocardium was viable, and normal myocardial oxidative metabolism, reflecting the recovery of the left ventricular function.