Background: advance care planning (ACP) allows a patient to state their preferences for care, so that if in future they cannot make decisions their wishes are known. Our aim was to review systematically the effectiveness of ACP interventions in people with cognitive impairment and dementia. Methods: systematic searches of key electronic databases, supplemented by hand searches of reference lists and consultation with experts. Two independent reviewers undertook screening, data extraction and quality assessment. Results: four studies were included; three allocated providers randomly to intervention or control arm. All took place in nursing homes. Three studies reported formal processes of capacity assessment, only up to 36% of participants were judged to have capacity. Three studies reported positive findings in terms of documentation of patient preferences for care. Two studies reported significant reductions in hospitalisation rates; a third found increased use of hospice services in the intervention group. A meta-analysis could not be carried out due to heterogeneity of outcome measures. Conclusions: there is limited evidence for the effectiveness of ACP in people with cognitive impairment/dementia in terms of ACP documentation and health-care use. In terms of capacity to discuss ACP, nursing home settings may be too late for people with dementia.