The authors attempted to elucidate the correlation of tumor cell density within the brain in glioma patients and T1-, T2-relaxometry and ADC. First, an exploratory study compared T1-, T2-relaxometry, and ADC with 11C-methionine PET followed by a validation study using intraoperative stereo-tactically obtained tissues. A range of T1 values indicative of high cell density was identified, which finding was confirmed by stereotactic tissue sampling. For T2 values and ADC, however, no statistically significant correlation was confirmed regarding tumor cell density. The proposed technique was further able to create predictive tumor cell density map by T1 supplemented by T2 values.