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Purpose: To find out if single-photon emission computed tomography (SPECT) and (123)I-subtraction can enhance the findings of (99m)Tc-methoxyisobutylisonitrile (MIBI) scintigraphy for the preoperative localization of parathyroid (PT) tumors., Methods: Among the 111 consecutive patients who underwent preoperative planar (99m)Tc-MIBI scintigraphy for hyperparathyroidism (HPT), 64 underwent delayed SPECT, and 17 underwent (123)I-subtraction. Two independent blinded experts scored the topographical localization, diagnostic confidence, and impact of each diagnostic modality on the surgical strategy., Results: For adenomas, (99m)Tc-MIBI scintigraphy had a sensitivity of 77% with a positive predictive value (PPV) of 83%. SPECT did not affect the sensitivity or PPV, but it increased the diagnostic confidence and changed the surgical strategy in 21% of the patients. (123)I-subtraction increased the sensitivity from 64% to 82%, but decreased the PPV from 88% to 82%. In hyperplastic glands, (99m)Tc-MIBI scintigraphy had a sensitivity of 47% and a PPV of 95%. When (99m)Tc-MIBI scintigraphy was combined with SPECT and (123)I-subtraction, the results were 44%/10% and 52%/92%, respectively. Both SPECT and (123)I-subtraction decreased the diagnostic confidence., Conclusions: Adding SPECT to (99m)Tc-MIBI scintigraphy improved the surgical decision for parathyroid adenomas. The addition of (123)I-subtraction was of limited value. For hyperplastic glands, (99m)Tc-MIBI scintigraphy was relatively ineffective, even with the addition of SPECT or (123)I-subtraction.