Alzheimer's disease (AD), dementia with Lewy bodies, frontotemporal dementia (FTD), and Huntington's disease (HD) are the main neurodegenerative causes of dementia. Causes and mechanisms of these diseases remain elusive. Neuroinflammation is increasingly emerging as an important pathological factor in their development. Positron emission tomography (PET) using [11C]PK11195 represents a method of visualizing the microglial component of neuroinflammation via the translocator protein (TSPO) and we discuss the valuable insights this has yielded in neurodegenerative diseases. We discuss the limitations of this method and the development of second generation TSPO PET ligands which hope to overcome these limitations. We also discuss other methods of visualizing neuroinflammation and review the state of current dementia treatments targeted at neuroinflammation. It is our view that a multimodal investigation into neuroinflammation in AD, Parkinson's disease dementia, FTD and HD will yield valuable pathological insights which will usefully inform development of therapeutic targets and biomarkers.