The aim of the study is to assess the relationship between T2* magnetic resonance imaging (MRI) values and age, serum ferritin level, left ventricular ejection fraction (LVEF), splenectomy status, and to identify appropriate modifications to chelation therapy based on T2* MRI results of children with thalassaemia major. Sixty-four patients with thalassaemia major (37 girls/27 boys) older than 8 years of age were enrolled in the study. Based on the first T2* MRI, the patients' myocardial iron depositions were classified into three groups: T2* MRI <10 ms (high risk group), T2* MRI 10-20 ms (medium-risk group) and T2* MRI >20 ms (low-risk group). There was no significant relationship between T2* MRI value and ages, serum ferritin levels and splenectomy status of thalassaemia major patients. The mean LVEFs were 60, 75, and 72.5 % in the high-, medium-, and low-risk groups, respectively (P = 0.006). The mean cardiac iron concentrations calculated from the T2* MRI values were 4.96 ± 1.93, 1.65 ± 0.37, and 0.81 ± 0.27 mg/g in the high-, medium-, and low-risk groups, respectively. Chelation therapies were re-designed in 24 (37.5 %) patients according to cardiac risk as assessed by cardiac T2* MRI. In conclusion, until recently, T2* MRI has been employed to demonstrate cardiac siderosis without a direct relationship with the markers used in follow-up of patients with thalassaemia. However, modifications of chelation therapies could reliably be planned according to severity of iron load displayed by T2* MRI.