Radiation-induced brain perfusion changes after radiotherapy have not been studied extensively with DSC-MRI. Tumour perfusion is often normalised to contralateral normal-appearing white matter, why knowledge about radiation effects on perfusion in normal brain tissue is essential. Ten patients were examined with DSC-MRI at 1.5 T before and repeatedly after RT. Multiple volumes were drawn in normal brain tissue. Radiation dose for all volumes were available. Significant CBV and CBF decrease after radiotherapy was visible in grey matter volumes and showed tendency to recover. High radiation dose regions should be avoided when normalising DSC-MRI derived tumour perfusion values.