High-resolution diffusion-weighted imaging (DWI) has the potential to improve the specificity of breast MRI. In this work a method is proposed for 3D isotropic DWI of the whole breasts. Three breast DWI datasets were acquired using a readout-segmented DW-EPI sequence (rs-EPI) with thick slices (3 mm) and 1mm-shifts in the slice direction. A high isotropic resolution (1x1x1 mm3) DWI dataset was reconstructed using a super-resolution reconstruction (SRR) on the low-resolution anisotropic acquisiitons, with different regularization schemes (Tikhonov and Beltrami, an edge-preserving constraint). This study shows the benefit of this strategy compared to native acquisitions with 1 mm slice thickness. A quantitative SNR evaluation is presented.