Survival after diagnosis of brain tumours is determined by several factors: performance status, primary diagnosis and extent of the extracranial (primary tumour) disease as well as age. The assessment of the overall prognosis of the patient is one of the key elements in therapy planning. For primary central nervous system (CNS) tumours, a crucial question is the pre-surgical estimation of tumour margins to allow for adequate safety-margins limiting excess iatrogenic healthy brain tissue removal. On follow-up, the differentiation between cancer progression from pseudo-progression poses one of the greatest challenges in longitudinal brain tumour therapy assessment. MRF has the potential to provide valuable information in both cases: differentiating the active tumour boundary from the surrounding viable tissue and quantifying effective therapy via a measured reduction in IFP. In patients with multiple metastases, currently whole brain radiation therapy (WBRT) is standard of care, while up to three metastases can be treated with surgery or stereotactic radiosurgery (SRS). Here, MRF may enable the decision whether WBRT could be spared. MRF’s application after surgical or radiosurgical treatment of single lesions provides information whether the tumour boarders of the resection cavity are free of force-exerting regions. In cases of a successfully treated metastasis, WBRT might be withheld. Thus, long-term toxicity of WBRT in terms of leukoencephalopathy, atrophy, radiation necrosis or cerebrovascular disease can be avoided in patients with a good prognosis. The quality of life during the prolonged survival of these patients will not be diminished by cognitive side effects of this treatment. We think that MRF might also play a role in the screening of normal appearing brain parenchyma and might be capable of detecting occult very small metastases as they reveal themselves via focal “hot-spots” of otherwise unexplainable forces.