Aim: To report a study of the relationship between person-centred care and ability to perform activities of daily living, quality of life, levels of pain, depressive symptoms, and agitated behaviours among residents with dementia in residential care facilities. Background: Standardized measurements of person-centred care have not previously been used to investigate the relationship between person-centred care and well-being for residents with dementia in residential aged care units. Design: This study had a cross-sectional design. Method: Staff and resident surveys were used in a sample of 1261 residents with dementia and 1169 staff from 151 residential care units throughout Sweden. Valid and reliable scales were used to measure person-centredness and ability to perform activities of daily living, quality of life, levels of pain, depressive symptoms, and agitated behaviours in residents. All data were collected in May 2010. Findings: Person-centred care was correlated with residents' ability to perform activities of daily living. Furthermore, residents in units with higher levels of person-centred care were rated as having higher quality of life and better ability to perform activities of daily living compared with residents in units with lower levels of person-centred care. Conclusions: There seems to be a relationship between person-centredness, residents' ability to perform activities of daily living, and residents' quality of life. Further studies are needed to explain the variation of person-centredness between units and the extent and ways this might impact on the quality of life and well-being of frail older residents with cognitive impairments in clinical practice. © 2013 Blackwell Publishing Ltd.