Color Doppler ultrasound (US) was performed in 153 patients (including 102 with lung cancer and 51 with benign lesions) to assess pulsatile flow signals in thoracic lesions. The values of resistive index (RI) and pulsatility index (PI) of color Doppler US pulsatile flow signals in lung cancers and benign lesions were measured, analyzed, and compared. In the enrolled 153 patients with thoracic lesions, 61 lung cancers and 34 benign lesions had detectable color Doppler US pulsatile flow signals, and lung cancers had lower RI and PI values than benign lesions (RI: 0.70+/-0.03 vs. 0.79+/-0.04, p < 0.05; PI: 1.61+/-0.15 vs. 2.44+/-0.25, p < 0.005). However, overlapping RI and PI values in lung cancers and benign lesions somewhat limited color Doppler US pulsatile flow signals to differentiate lung cancers from benign lesions. Further analysis of RI and PI values in subgroups of lung cancers [squamous cell carcinoma (SCC, n = 34), adenocarcinoma (AC, n = 18), and small-cell lung cancer (SCLC, n = 6)] and benign lesions [cavitary benign lesions (CBL, n = 8), and noncavitary benign lesions (NCBL, n = 26)] revealed that all different cell types of lung cancers (SCC, AC, and SCLC), indeed, had lower RI and PI values than NCBL (for RI, all p < 0.01; for PI, all p< or =0.001). Moreover, the mean RI and PI values showed a significant incremental decrease from NCBL (mean RI, PI = 0.88, 2.94) toward SCC and AC (for SCC, mean RI, PI = 0.71, 1.68; for AC, mean RI, PI = 0.68, 1.67) and, finally, to SCLC (mean RI, PI = 0.62, 1.05). In contrast, CBL had relatively lower RI and PI values than AC and SCLC (for CBL, mean RI, PI = 0.53, 0.80; both p > 0.05 for RI and PI), and even a significant difference from SCC (p < 0.05 for RI and PI). We conclude that color Doppler US pulsatile flow signal is somewhat limited to differentiate lung cancers from benign lesions, but provides a noninvasive in vivo model to assess the neovascularity intensity of lung cancers.