cardiac diseases and/or severe arrhythmias. One of the side effects of amiodarone therapy is thyroid dysfunction, which is observed in about 20% of patients. The thyroid dysfunction may present with various forms: from subclinical changes in hormone levels to amiodaroneinduced thyrotoxicosis (AIT) and amiodarone-induced hypothyroidism (AIH). Material and methods: We reported six patients in the age range from two weeks to 14 years, with complex congenital cardiac diseases and severe arrhythmias, who developed amiodarone-induced thyroid dysfunctions: thyrotoxicosis or hypothyroidism or both together. The clinical signs and symptoms of all thyroid dysfunctions were atypical, most patients presented with an aggravation of heart insufficiency. Our patients with thyrotoxicosis were treated with combined therapy including thionamides and corticosteroids due to the presentation of mixed-identified type of AIT. Results: Currently, five patients (one patient’s status is unknown) are in biochemical and clinical euthyreosis; however, in one of them it was impossible to discharge amiodarone treatment. Three of them are still treated with levothyroxine, and two do not need thyroid treatment. Conclusions: Amiodarone-induced thyroid dysfunction is usually atypical; therefore, monitoring of thyroid status before, during, and after amiodarone is demanded. AIH could significantly influence the development of the child, while AIT could significantly deteriorate the clinical status of children with complex cardiac diseases. Early and proper diagnose of AIT and AIH allows the introduction of immediate and appropriate treatment considering the cardiac condition of the young patient.