The study is to quantitatively compare the diagnostic ability of ADC in distinguishing three types of parotid tumor between the ADC measurement on slice with the largest tumor and whole tumor. This retrospective study enrolled 13 patient for each PMAs, WTs and MTs. All participants underwent 1.5-T fat-saturated EP-DWI. Our results show that ADC and AUC on largest slice and whole tumor were similar in three tumors. ADC of the slice with the largest tumor, which tumor size over 1/3 whole tumor volume, could instead the ADC of whole tumor to diagnosis the PMA, WT and MT in parotid gland.