Vibro-acoustography (VA) is an emerging imaging technology. In this method, radiation force of ultrasound is used to vibrate tissue at low (kHz) frequencies. The resulting vibration produces an acoustic field that is detected by a sensitive hydrophone. VA can provide detail information at high resolution that is not available from conventional Bmode ultrasound (US) imaging. Here, we compare VA and US in breast imaging. An experimental VA system was used to image breasts of patients with known lesions of various kinds. Results were compared to US. Image quality was assessed based on contrast, resolution, lesion boundaries, and artifacts. VA images displayed breast cysts with well-defined borders. Fibroadenomas were seen with identifiable texture, and in some cases, with enhanced boundaries. Post-lumpectomy scars were displayed with characteristic structure. Some malignant masses were seen with identifiable spiculations. Compared to US, VA images were speckle free, had high contrast and high signal to noise ratio. Microcalcifications were particularly visible with VA. The combination of features offered by VA, such as lack of image speckle, enhanced lesion boundaries, and sensitivity to microcalcifications, are important advantages of VA over US for breast imaging. It is concluded that VA may become a choice modality for breast imaging.