Serum ferritin (SF) and liver iron concentration (LIC), as measured by SQUID biosusceptometry, were assessed in a convenience sample of transfusion independent thalassemia patients (nTx-Thal, n = 26), regularly transfused thalassemia (Tx-Thal, n = 89), or sickle cell patients (SCD, n = 45) to investigate the severity of iron overload and the relationship between SF and LIC in nTx-Thal compared to SCD and Tx-Thal. SF correlated with LIC (RS = 0.53, P < 0.001), but was found to be a poor predictor for LIC. SF was significantly lower (P < 0.001) in nTx-Thal patients than in other groups, despite similar LIC values. The SF-to-LIC ratio was significantly lower in nTx-Thal compared to Tx-Thal and SCD patients (median of 0.32, 0.87, and 1.2, respectively: P < 0.001). Due to underestimation of LIC by ferritin levels, chelation treatment may be delayed or misdirected in patients with thalassemia intermedia. Pediatr Blood Cancer 2007;49:329–332. © 2007 Wiley-Liss, Inc.