DWI is a non-invasive technique that represents the biological character of the mainly Brownian movement of protons in bulk water molecules in vivo. To evaluate the role of the apparent diffusion coefficient (ADC) value in different molecular subtypes of invasive breast cancer. Prospective study of 30 patients with mean age of 45.5, diagnosed with breast cancer. Evaluated during the period from September 2018 to September 2019. DWIs and quantitative analysis of ADC maps was done, the mean ADC value of the breast lesions was calculated and correlated with the different prognostic factors. There was a significant difference between the mean ADC value of luminal A and HER-2 positive groups (p= 0.001); and between luminal B and HER-2 positive groups (p= 0.001).There was a significant difference between the mean ADC value of luminal A and TNBC groups (p= 0.001); and between luminal B and TNBC groups (p= 0.001).There was a significant difference between the mean ADC value of HER-2 positive and TNBC groups (p= 0.001); However, there was no statistical difference between luminal A and luminal B groups (p= 1).Lower ADC value is noted with high Ki-67 tumours (0.91 x 10 -3 mm 2) , while high ADC value is noted in low Ki-67 tumours (0.99 x 10 -3 mm 2), Yet no statistically significant difference is noted in-between (p=0.365). . DWI is a contrast-free modality that allows for both morphological and quantitative analysis. ADC value may not be the proper modality to use for identifying the degree of aggressiveness in breast cancer, yet it could be a good predictor of breast cancer cells that would respond to chemotherapy.