Purpose We assessed the lesion detection performance of the dual-tracer parathyroid SPECT imaging using the joint reconstructionmethod. Materials and Methods Thirty-six noise realizations were created from SPECT projections collected from an in-house neckphantom to emulate 99mTc-pertechnetate/99mTc-sestamibi parathyroid SPECT datasets. Difference images representing parathyroidlesions were reconstructed using the subtraction and the joint methods whose corresponding optimal iteration wasdefined as the iteration which maximized the channelized Hotelling observer signal-to-noise ratio (CHO-SNR). The jointmethod whose initial estimate was derived from the subtraction method at optimal iteration (the joint-AltInt method) wasalso assessed. In a study of 36 patients, a human-observer lesion-detection study was performed using difference images fromthe three methods at optimal iteration and the subtraction method with four iterations. The area under the receiver operatingcharacteristic curve (AUC) was calculated for each method. Results In the phantom study, both the joint-AltInt method and the joint method improved SNR compared to the subtractionmethod at their optimal iteration by 444% and 81%, respectively. In the patient study, the joint-AltInt method yielded thehighest AUC of 0.73 as compared with 0.72, 0.71, and 0.64 from the joint method, the subtraction method at optimal iteration,and the subtraction method at four iterations. At a specificity of at least 0.70, the joint-AltInt method yielded significantlyhigher sensitivity than the other methods (0.60 vs 0.46, 042, and 0.42; p < 0.05). Conclusions The joint reconstruction method yielded higher lesion detectability than the conventional method and holdspromise for dual-tracer parathyroid SPECT imaging.