We aimed to investigate the accuracy of high resolution-DWI (HR-DWI) using rs-EPI in estimating residual lesion size after neoadjuvant systemic treatment (NST) using pathological information as a reference. Diagnosis of pCR by two readers were accurate in 83/79 % with HR-DWI, while 50/46 % on HR-CE MRI. Spearman’s correlation coefficient between size on pathology and that on HR-DWI were 0.79 (p<0.0001), indicating strong correlations. Spearman’s correlation coefficient between size on pathology and that on HR-CE-MRI were 0.68 (p<0.0001). Using HR-DWI, residual lesions were depicted with good agreement with the pathology without using contrast agent.