The purpose of this study was to evaluate whether 3D power Doppler ultrasonography is capable of accurately differentiating between uterine leiomyoma and adenomyosis prior to surgery. This study comprised 95 women with a benign uterine mass admitted for a total abdominal hysterectomy. All subjects underwent a trans-abdominal 3D power Doppler ultrasonographic examination prior to surgery. The examination evaluated tumor size, tumor volume, vascular location (location), vascular index (VI), flow index (FI), and vascular-flow index (VFI). Results reveal that patients with uterine leiomyoma had significantly higher VI (U = 375.50, p < 0.001), FI (U = 386, p < 0.001), and VFI (U = 374.5, p < 0.001) levels than did patients with adenomyosis. A significant difference in vascular location was also noted between cases of uterine leiomyoma and adenomyosis (Fisher exact test, p < 0.001). The results suggest that 3D power Doppler ultrasonography could be used to more effectively differentiate between uterine adenomyosis and leiomyoma, with potential widespread applicability in the near future.