Imaging-based markers of treatment response are increasingly being used in studies of brain-tumour therapies, for evaluating novel treatments and further understanding of existing therapies. An ultimate goal of these studies is to identify pre- or early-stage treatment imaging biomarkers that enable prediction of subsequent treatment response. We hypothesised that pretreatment MRI-based measurements of tumoural perfusion may provide a suitable imaging-based biomarker for prediction of subsequent treatment response and evaluated this in a group of nine high-grade glioma patients undergoing dexamethasone treatment. A strong positive correlation was observed between tumoural blood flow (R(2)=0.90, p<0.001) and tumoural blood volume (R(2)=0.76, p=0.002), and subsequent treatment response as measured by alterations in tumour leakage properties. These preliminary results indicate that measurements of tumoural perfusion may provide useful imaging biomarkers for predicting treatment response to dexamethasone and would therefore also be worth evaluating in newer emerging therapies.