Background: In a prospective study, we compared power Doppler with and without contrast medium in the depiction of vascularity for the characterization of hyperechoic renal lesions. Methods: Forty-one hyperechoic renal expansive lesions (29 benign, 12 malignant) in 32 patients were studied with power-Doppler ultrasonography before and after administration of an echo-enhancing agent (Levovist Schering AG, Berlin, Germany). Vascular architecture of the lesions was categorized into five different patterns. Results: Power Doppler ultrasonography showed vascular structures in 25 lesions. The study enhanced with Levovist showed vascularity in eight of 16 lesions not seen on the unenhanced study. The characterization of vascular patterns with unenhanced power Doppler ultrasonography improved diagnostic accuracy compared with gray-scale ultrasonography (59% vs. 32%). The combination of B mode and power Doppler produced even greater diagnostic accuracy (78%), independent of the administration of echo-enhancing agent. Levovist administration was useful in the differential diagnosis between pseudotumor and neoplasm. Conclusion: The use of songraphic contrast agent did not increase the diagnostic accuracy of power Doppler in the differential diagnosis of hyperechoic renal lesions but was advantageous for the characterization of suspected pseudomasses.