•BBB breakdown is a major driving force in dementia pathology.•DCE-MRI is the most advanced method to investigate BBB leakage in the living human and rodent brain.•Many different DCE-MRI techniques and imaging processing methods exist.•Detecting subtle BBB breakdown using DCE-MRI can be challenging. Alzheimer’s disease (AD) and cerebral small vessel disease (cSVD) are the two main causes of dementia with blood–brain barrier (BBB) breakdown being a common contributor. Recent advances in neuroimaging techniques offer new possibilities to understand how the brain functions in health and disease. This includes methods such as dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) which allows the detection of subtle regional changes in the BBB integrity. The purpose of this work is to provide a review on the recent DCE-MRI findings of subtle BBB leakage focusing on cSVD and AD, including both clinical and pre-clinical studies. Despite being widely used and well-established, we also highlight some of the DCE-MRI challenges and pitfalls faced in the context of dementia inherent to the subtle nature of BBB impairment.