Background The increase of neoadjuvant treatment for breast cancer creates a capacity challenge as response evaluation by magnetic resonance imaging (MRI) is a limited resource. Contrast-enhanced ultrasound (CEUS) has been proposed as an alternative imaging strategy. Purpose To get experience with examination of malignant breast tumors with CEUS and evaluate the potential for future use in response evaluation of neoadjuvant treatment. Material and methods In this pilot study, the dynamic contrast-enhancement of ultrasound and MRI examinations were analyzed in 14 women with histologically verified breast cancer. Results Analysis of the time intensity curve of CEUS demonstrated the difference between tumor and normal tissue. The peak intensity was five times higher in tumor tissue (mean increase 397%, 95% CI 250–545). The curve was steeper for tumor tissue (mean 1.76, 95% CI 1.26–2.26) than for normal tissue (mean 0.43, 95% CI 0.24–0.62). Conclusion CEUS is a feasible method of examining blood flow in malignant breast tumors.