Color Doppler ultrasound (US) is a very powerful imaging tool that can simultaneously display blood flow information and Doppler spectral analysis. This imaging modality, for the first time, provides an opporturnity to assess pulmonary blood flow and perfusion noninvasively. Color Doppler US has many potential applications in diseases of the chest. Color Doppler imaging is useful in assisting the diagnosis of pulmonary arterio-venous malformation and pulmonary sequestration. The ‘fluid color sign’ can be used to detect minimal effusion amenable to thoracentesis. Color Doppler US can be utilized to assess the angiogenesis of a lung tumor and is helpful in differentiating a malignant tumor from a benign one. Color Doppler US can be used to guide a transthoracic needle biopsy and improve the safety of this invasive procedure. Color Doppler US can demonstrate the vascular patterns and assess the regional hemodynamic changes of a pulmonary consolidation. The information of spectral wave analysis is helpful for understanding the underlying etiology of a pulmonary consolidation. Color Doppler US is useful in assessing the perfusion and reperfusion status of a pulmonary infarction. There are still other potential applications of this new technique in chest diseases that may need further exploration.