Diffusion-weighted imaging (DWI) has been applied to fetal MRI and provides important information in evaluating the microstructures. Apparent diffusion coefficient (ADC) value is derived from DWI sequence. The aim of this study is to compare ADC values of brain in surviving fetus of one fetus demise with normal fetuses using diffusion weighted imaging and to find the differences and underlying cerebral microstructure changes. Decrease of ADC values were detected in surviving fetus of one twin demise. DWI and ADC values are very useful for detecting underlying changes, even changes of signal are not visible on conventional sequences.