The purpose of this study was to reassess the role of MRI in 3 cases of cystosarcoma phyllodes. Three patients with a palpable large lump were studied with mammography, ultrasonography and MRI. In the 3 patients mammography showed a nonspiculate soft-tissue mass while a hypoechoic lobulated mass with cystic areas was visualized on sonography. Dynamic MRI demonstrated a multi-lobulated lesion rapidly and markedly enhanced on dynamic studies of contrast-enhanced T1-weighted imaging. T2WI showed inhomogeneous signal intensity with a hypointense area and internal septation in the solid portion. MRI enabled complete visualization of the tumor even in the region close to the chest wall, as well as clear delineation against the healthy glandular tissue.