Background Currently, multi-parametric prostate MRI (mpMRI) consists of a qualitative T-2, diffusion weighted, and dynamic contrast enhanced imaging. Quantification of T-2 imaging might further standardize PCa detection and support artificial intelligence solutions. Purpose To evaluate the value of T-2 mapping to detect prostate cancer (PCa) and to differentiate PCa aggressiveness. Study Type Retrospective single center cohort study. Population Forty-four consecutive patients (mean age 67 years; median PSA 7.9 ng/mL) with mpMRI and verified PCa by subsequent targeted plus systematic MR/ultrasound (US)-fusion biopsy from February 2019 to December 2019. Field Strength/Sequence Standardized mpMRI at 3 T with an additionally acquired T-2 mapping sequence. Assessment Primary endpoint was the analysis of quantitative T-2 values and contrast differences/ratios (CD/CR) between PCa and benign tissue. Secondary objectives were the correlation between T-2 values, ISUP grade, apparent diffusion coefficient (ADC) value, and PI-RADS, and the evaluation of thresholds for differentiating PCa and clinically significant PCa (csPCa). Statistical Tests Mann-Whitney test, Spearman's rank (r(s)) correlation, receiver operating curves, Youden's index (J), and AUC were performed. Statistical significance was defined as P < 0.05. Results Median quantitative T-2 values were significantly lower for PCa in PZ (85 msec) and PCa in TZ (75 msec) compared to benign PZ (141 msec) or TZ (97 msec) (P < 0.001). CD/CR between PCa and benign PZ (51.2/1.77), respectively TZ (19.8/1.29), differed significantly (P < 0.001). The best T-2-mapping threshold for PCa/csPCa detection was for TZ 81/86 msec (J = 0.929/1.0), and for PZ 110 msec (J = 0.834/0.905). Quantitative T-2 values of PCa did not correlate significantly with the ISUP grade (r(s) = 0.186; P = 0.226), ADC value (r(s) = 0.138; P = 0.372), or PI-RADS (r(s) = 0.132; P = 0.392). Data Conclusion Quantitative T-2 values could differentiate PCa in TZ and PZ and might support standardization of mpMRI of the prostate. Different thresholds seem to apply for PZ and TZ lesions. However, in the present study quantitative T-2 values were not able to indicate PCa aggressiveness. Level of Evidence 2 Technical Efficacy Stage 2