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Background: This study sought to compare the intensity of early-phase myocardial uptake of two phosphonate-based radiotracers, 99m Tc-hydroxymethylene diphosphonate (HMDP) and 99m Tc-3,3-diphosphono-1,2-propanodicarboxylic acid (DPD), in patients with hereditary transthyretin-related cardiac amyloidosis (TTR-CA)., Methods: Six patients with biopsy-proven diagnosis of TTR-CA and characteristic amyloid fibril composition underwent early-phase 99m Tc-HMDP myocardial scintigraphy as part of their routine workup; they were later assessed by 99m Tc-DPD scintigraphy after having signed informed written consent. Heart-to-mediastinum-ratio was measured at both time points as well as regional distribution on 17-segment analysis., Results: All patients had an H/M ratio >1.28 on both imaging. 99m Tc-DPD uptake was slightly higher than 99m Tc-HMDP uptake in 3 patients, but no statistical difference was found (P = 0.13). Regional distribution of the two radiotracers was well correlated on bull's eyes analysis, with only slight underestimation of 99m Tc-DPD uptake in the anterior/apical segments, compared with 99m Tc-HMDP., Conclusion: 99m Tc-HMDP and 99m Tc-DPD show comparable myocardial uptake intensity on early-phase scintigraphy and can be used alternatively for the diagnosis of TTR-CA.