Background Myocarditis is a common, potentially life-threatening disease that presents a wide rang of symptoms in children, as an important underlying etiology of other myocardial diseases such as dilated and arrhythmogenic right ventricular cardiomyopathy. The incidence of nonfatal myocarditis is probably greater than that of the one actually diagnosed, which is the result of the challenges of establishing the diagnosis in standard clinical settings. Currently, no single clinical or imaging finding confirms the diagnosis of myocarditis with absolute certainty. Historically, clinical exam, electrocardiogram (ECG), serology and echocardiography had an unsatisfactory diagnostic accuracy in myocarditis. Endomyocardial biopsy remains as a widely accepted standard, but may not be suitable for every patient, especially for those with less severe disease. Our aim was to find the changes in cardiovascular magnetic resonance (CMR) imaging of children with myocarditis diagnosed by clinical criteria. Methods We studied 25 children (18 male, 7 female; aged from 5-17 years) with diagnosed myocarditis by clinical criteria. CMR included function analyses, T2-weighted imaging, T1-weighted imaging before and after i.v. gadolinium injection (early gadolinium enhancement (EGE) and late gadolinium enhancement (LGE)). Results The T2 ratio was elevated in 21 children (84%, 11 in anterolateral (44%), 5 in inferolateral (20%), and 5 in septum (20%)), EGE was present in 9 children (36%, 3 in anterolateral (12%), 4 in inferolateral (20%), and 2 in septum (8%)), and LGE was present in 5 children (20%, 2 in anterolateral (8%), 1 in inferolateral (4%), 1 in septum (4%), and 1 in midwall of left ventricular (LV) wall). In 9 children (36%), two (or more) out of three sequences (T2, EGE, LGE) were abnormal. Conclusions The CMR findings in children with clinically diagnosed myocarditis vary within the groups, including regional or global myocardial signal increase in T2-weighted images, EGE and LGE in T1-weighted images. The T2 ratio elevation is the most common CMR finding. Children with mild cardiac symptoms may also appear serious myocardial injuries.