BACKGROUND Diagnosis of cardiac masses is still challenging by echocardiography and distinguishing tumors from thrombi has important therapeutical implications. We sought to determine the diagnostic value of real-time perfusion echocardiography (RTPE) for cardiac masses characterization. METHODS We prospectively studied 86 patients, 23 with malignant tumors (MT), 26 with benign tumors (BT), 33 with thrombi and 6 with pseudotumors who underwent RTPE. Mass perfusion was analyzed qualitatively and blood flow volume (A), blood flow velocity (β), and microvascular blood flow (A x β) were determined by quantitative RTPE. RESULTS Logistic regression models showed that the probability of having a tumor increased by 15.8 times with a peripheral qualitative perfusion pattern, and 34.5 times with a central perfusion pattern, in comparison with the absence of perfusion. Using quantitative RTPE analysis, thrombi group had parameters of blood flow lower than tumor group. A values for thrombi, MT, and BT were 0.1 dB (0.01-0.22), 2.78 dB (1-7) and 2.58 dB (1.44-5), respectively; p < 0.05, while A x β values were 0.0 dB/s(-1) (0.01-0.14), 2.00 dB/s(-1) (1-6), and 1.18 dB/s(-1) (0.52-3), respectively; p < 0.05. At peak dipyridamole stress, MT had greater microvascular blood volume than BT [A = 4.18 dB (2.14-7.93) versus A = 2.04 dB (1.09-3.55); p < 0.05], but no difference in blood flow [Axβ = 2.46 dB/s(-1) (1.42-4.59) versus Axβ = 1.55 dB/s [1] (0.51-4.08); p = NS]. An A value >3.28 dB at peak dipyridamole stress predicted MT (AUC = 0.75) and conferred 5.8-times higher chance of being MT rather than BT. CONCLUSIONS RTPE demonstrated that cardiac tumors have greater microvascular blood volume and regional blood flow when compared with thrombi. Dipyridamole stress was useful in differentiating MT from BT.