Because left ventricular (LV) diastolic dysfunction is frequently the earliest indicator of LV dysfunction in patients with heart failure, the estimation of LV diastolic function is very important. On the other hand, electrocardiography (ECG)-gated technetium (Tc) -99m tetrofosmin single-photon emission computed tomography (SPECT) has been reported to be a useful method for evaluation of LV function. The objective of this study was to examine the usefulness of ECG-gated Tc-99m tetrofosmin SPECT in terms of estimation of cardiac diastolic function. Consecutive 145 patients underwent an ECG-gated Tc-99m tetrofosmin SPECT to estimate systolic and diastolic LV function, and were compared with those evaluated by ultrasound echocardiography (UCG). LV end-diastolic volume, LV end-systolic volume, and LV ejection fraction values obtained by quantitative gated SPECT (QGS) showed significant positive linear correlations with those obtained by UCG. All 145 patients were classified into 3 groups according to diastolic function estimated by UCG. The first-third mean filling rate (1/3 MFR) and peak filling rate (PFR) that revealed the LV diastolic function of the group B (normal systolic function and mild diastolic dysfunction) patients (1.01 ± 0.35, 1.85 ± 0.57) were both significantly lower than those of the group A (normal systolic and diastolic function) patients (1.43 ± 0.37, 2.43 ± 0.56). The 1/3 MFR and PFR of the group C (moderate ~ severe systolic and diastolic dysfunction) patients (0.47 ± 0.34, 0.92 ± 0.62) were also significantly lower than those of the group A and B patients. QGS may be a useful method for the evaluation of cardiac systolic and diastolic function, especially in patients with normal systolic function and diastolic dysfunction.