Other ; This is the final version of the article. It first appeared from the Royal College of Psychiatrists via http://dx.doi.org/10.1192/bjp.bp.116.190165 ; Abstract ; We studied neuroinflammation in individuals with late-life depression, as a risk factor for dementia, using [$^{11}$C]PK11195 positron emission tomography (PET). Five older participants with major depression and 13 controls underwent PET and multimodal 3T magnetic resonance imaging (MRI), with blood taken to measure C-reactive protein (CRP). We found significantly higher CRP levels in those with late-life depression and raised [$^{11}$C]PK11195 binding compared with controls in brain regions associated with depression, including subgenual anterior cingulate cortex, and significant hippocampal subfield atrophy in cornu ammonis 1 and subiculum. Our findings suggest neuroinflammation requires further investigation in late-life depression, both as a possible aetiological factor and a potential therapeutic target. ; Other ; The study was funded by the National Institute for Health Research (NIHR) Biomedical Research Centre and Biomedical Research Unit in Dementia based at Cambridge University Hospitals NHS Foundation Trust and the University of Cambridge. J.B.R. is supported by the Wellcome Trust (103838).