Rationale and Objectives: Fat quantification accuracy using a commercial single-voxel high speed T₂-corrected multi-echo (HISTO) technique and its robustness to R₂* variations at 3.0 T, such as those introduced by iron in liver, has not been fully established. This study evaluated HISTO at 3.0 T and sought to reproduce results at 1.5 T. Methods: Phantoms were prepared with a range of fat content and R₂*. Data were acquired at 1.5 T and 3.0 T, using HISTO and a Dixon technique. Fat quantification accuracy was evaluated as a function of R₂*. The patient study included 239 consecutive patients. Data were acquired at 1.5 T or 3.0 T, using HISTO and Dixon techniques. The techniques were compared using Bland-Altman plots. Bias significance was evaluated using a one-sample t-test. Results: In phantoms, HISTO was accurate within 10% up to a R₂* of 100 s⁻¹ at both field strengths, while Dixon was accurate within 10% where R₂* was accurately quantified (up to 350 s⁻¹ at 1.5 T, and 550 s⁻¹ at 3.0 T). In patients, where R₂* was <100 s⁻¹, fat quantification from both techniques agreed at 1.5 T ( P = .71), but not at 3.0 T ( P = .007), with a bias <1%. Conclusion: Results suggest that HISTO is reliable when R₂* is <100 s⁻¹, corresponding to patients with at most mild liver iron overload, and that it should be used with caution when R₂* is >100 s⁻¹. Dixon should be preferred for hepatic fat quantification due to its robustness to R₂* variations.