The mean and minimal ADC values of HER2 (3+) gastric cancers were significantly higher than those of HER2-negative (0) tumors (1.295 ± 0.290 vs. 0.934 ± 0.215, 1.164 ± 0.349 vs. 0.861 ± 0.217 × 10−3 mm2/s, P = 0.004, 0.016, respectively). This evidence concerns the gene ERBB2 and gastric cancer.