DWI, which is less affected by the state of the background mammary gland, has sufficient capability to diagnose invasive, noninvasive, and invasive lobular carcinoma. DWI is different from conventional methods based on blood flow data and has the potential to provide useful information for the evaluation of NAC, which is considered to be insufficient at present. Having the ability to provide steady, high-resolution tissue images, DWI is expected to play an important role in future breast cancer diagnosis. DWI, however, is not a complete method of diagnosis. Limits exist in spatial resolution and problems with ADC. In consideration of these shortcomings, we need to apply DWI to clinical practice while taking advantage of its high contrast resolution.