Reliable insight about tumor microvasculature is important for monitoring of disease progression and treatment response. Derived from Dynamic Susceptibility Contrast MRI, transverse relaxation rates are used for vessel size estimation. In high grade glioma, these signals can artificially change by contrast agent extravasation through a disrupted Blood-Brain-Barrier. In this study the effect of applying Boxerman-Schmainda-Weisskoff leakage correction on vessel size estimation has been investigated on a group of 12 glioma patients. The result shows that in Contrast-Enhanced Tumor area applying leakage correction significantly and noticeably changes the vessel size measurements.