OBJECTIVE. Surgical intervention in the form of parathyroidectomy is generally considered only for severe secondary hyperparathyroidism (sHPT). However, correct location of the parathyroid glands before parathyroidectomy is a challenge. The purpose of this study was to compare the diagnostic value of early and delayed phase Tc-99m-sestamibi SPECT/CT in the detection of parathyroid tissue to guide operative treatment of patients with sHPT. SUBJECTS AND METHODS. Eighty patients with sHPT who were undergoing hemodialysis were evaluated preoperatively with dual-phase Tc-99m-sestamibi SPECT/CT parathyroid scintigraphy to locate parathyroid tissue before parathyroidectomy. The scintigraphic results were classified as positive or negative. The accuracy of Tc-99m sestamibi early and delayed phase SPECT/CT scintigraphy was determined. RESULTS. Early phase 99mTc-sestamibi SPECT/CT depicted 3.57 parathyroid glands (PTGs) and delayed phase Tc-99m-sestamibi SPECT/CT depicted 3.55 PTGs per study. The specificity of both early and delayed phase Tc-99m-sestamibi SPECT/CT in detecting PTGs was 100%. The Tc-99m-sestamibi SPECT/CT images of 7 of 80 patients showed positive findings in the delayed phase and negative findings in the early phase. The Tc-99m-sestamibi SPECT/CT images of 6 of 80 patients showed positive findings in the early phase and negative findings in the delayed phase. CONCLUSION. The results of our study indicate that both early and delayed phase Tc-99m-sestamibi SPECT/CT should be performed in the preoperative evaluation of hemodialysis patients with sHPT due to chronic kidney disease. Performance of both early and delayed phase Tc-99m-sestamibi SPECT/CT did not increase the radiation dose compared with the use of only the early or the delayed phase.