Résumé
This study evaluated the validity and reliability of the Montessori Assessment System.The Montessori Assessment System assesses preserved abilities in persons with moderate tosevere dementia. In this respect, this instrument provides crucial information for the developmentof effective person-centered care plans. A total of 196 persons with a diagnosis of dementiain the moderate to severe stages of dementia were recruited in 10 long-term care facilitiesin France. All participants completed the Montessori Assessment System, the ClinicalDementia Rating Scale and/or the Mini Mental State Examination and the Severe Impairment Battery-short form. The internal consistency and temporal stability of the MontessoriAssessment System were high. Additionally, good construct and divergent validity were demon-strated. Factor analysis showed a one-factor structure. The Montessori Assessment Systemdemonstrated satisfactory psychometric properties while being a useful instrument to assesscapabilities in persons with advanced stages of dementia and hence to develop person-centered plans of care.