Background: Tumor-infiltrating lymphocytes (TILs) are emerging as prognostic factors in early breast cancer and have shown to predict response to NAC, especially in triple-negative breast cancer (TNBC). However, it is not clear whether all intratumoral and stromal immune cells show the same predictive value or if there is a specific cell subtype involved in response and prognosis Methods: We retrospectively analyzed the diagnostic biopsies of breast cancer patients treated with NAC in our institution in the last 4 years. 3-4µm thick sections were subjected to immunohistochemistry using antibodies against CD3, CD4, CD8 and CD20. Intratumoral and stromal lymphocytes were measured and expressed in positive cells per mm². Every patient received chemotherapy with weekly paclitaxel and doxorubicin-cyclophosphamide and HER2 positive tumors were treated with trastuzumab. All patients received surgery. pCR was defined as no residual invasive tumor in the breast and the axilla. Descriptive statistics are reported as median (IQR, interquartile range) or mean (SD, standard deviation) for continuous variables, and as absolute or relative frequencies for categorical variables Results: From 144 evaluable specimens, 72 were estrogen-receptor and/or progesterone-receptor positive, 27 were TNBC and 45 were HER2 positive tumors. 70 pCR were documented. The expression of stromal CD3, CD4 and CD20 lymphocytes was significantly associated with pCR in all breast cancer subtypes: CD3 (28,00 [27,25], p < 0.001); CD4 (16,00 [23,75], p = 0.007); CD20 (2,50 [7,25], p = 0.046). In the subgroup analysis, both stromal CD3 (34,00 [24,00], p = 0.004), intratumoral CD3 (7,50 [19,50], p = 0.013), and intratumoral CD8 (3,00 [17,50], p = 0.041) lymphocytes were significantly associated with pCR in TNBC. In HER2 positive tumors stromal CD3 and CD4 were predictive of pCR ((26,00 [26,00], p < 0.001) and (16,00 [24,00], p = 0.042) respectively) Conclusions: Stromal CD3 lymphocytes are the most significant predictive factor of pCR in all breast cancer subtypes after NAC. In TNBC both intratumoral and stromal CD3 expression was associated with pCR.