Diffusion-weighted magnetic resonance imaging (DWI) can complement MRI of the prostate in the detection and localization of prostate cancer, particularly after previous negative biopsy. A total of 13 original reports and 2 reviews published in 2010 demonstrate that prostate cancer can be detected by DWI due to its increased cell density and decreased diffusiveness, either qualitatively in DWI images or quantitatively by means of the apparent diffusion coefficient (ADC). In the prostate, the ADC is influenced by the strength of diffusion weighting, localization (peripheral or transitional zone), presence of prostatitis or hemorrhage and density and differentiation of prostate cancer cells. Mean differences between healthy tissue of the peripheral zone and prostate cancer appear to be smaller for ADC than for the (choline + creatine)/citrate ratio in MR spectroscopy. Test quality parameters vary greatly between different studies but appear to be slightly better for combined MRI and DWI than for MRI of the prostate alone. Clinical validation of DWI of the prostate requires both increased technical conformity and increased numbers of patients in clinical studies.