Background. The aim of the present study was to investigate the relationships between personality and quality of life during the course of geriatric rehabilitation, against the background of Cloninger's biosocial theory of personality. Methods. All consecutive patients of a geriatric rehabilitation clinic during one year were evaluated at admission and discharge (N = 687) by means of the ''Vienna List'' (a newly developed questionnaire for the assessment of quality of life in patients with severe dementia), and two variants of the Temperament and Character Inventory. Results. Self-directedness showed the most general and highest impact on quality of life and successful rehabilitation. Conclusions. It is probable in old and very old individuals who are on their highest level of maturity that the character represents the most important regulatory system in the encounter with challenges of daily life, which necessitates rehabilitation.