Two male adolescents were admitted due to chest pain influenced by the respiratory movements. A lobar pneumonia caused by Mycoplasma pneumoniae, was radiographically and serologically diagnosed in the first patient (a 15-year-old boy) and a febrile diarrhea of unidentified etiology, despite repetitive stool cultures and serological assessments in the second one (a 19-year-old male). Both patients combined the aforementioned infectious conditions with outstanding thoracic pain the previous hours before admission, markedly elevated cardiac enzymes and ST-segment elevation in the inferior and left precordial leads with a normal coronary angiogram, thus composing a clinical setting highly indicative of acute myocarditis. Surprisingly however, the echocardiogram performed in both patients failed to reveal any regional or global wall motion abnormalities or even diastolic dysfunction and remained absolutely normal throughout their 3-month follow-up period. Cardiac MRI within 7 days, using T2-weighted and gadolinium-enhanced T1-weighted images demonstrated extensive focal contrast enhancement, consistent with acute inflammatory myocardial involvement. It can therefore be concluded that contrast MRI is a more sensitive method than the echocardiogram for the diagnosis of acute focal myocarditis.