There are many instruments assessing the wellbeing of staff, but far from all have been psychometrically investigated. When evaluating supportive interventions directed toward nurse assistants in residential care, valid and reliable instruments are needed in order to detect possible changes. The aim of the study was to investigate validity in terms of data quality, construct validity, convergent and divergent validity and reliability in terms of the internal consistency and stability of the Job Satisfaction Questionnaire, the Psychosocial Aspects of Job Satisfaction, the Strain in Dementia Care Scale (SDCS), and the Stress of Conscience Questionnaire (SCQ) in a residential care context. The psychometric properties of the instruments were investigated in terms of data quality, construct validity, convergent and divergent validity and reliability, including test-retest reliability, in a residential care context with a sample consisting of nurse assistants (n=114). The four instruments responded with different psychometric-related problems such as internal missing data, floor and ceiling effects, problems with construct validity and low test-retest reliability, especially when assessed on the item level. These problems were however reduced or disappeared completely when assessed for total and factor scores. From a psychometric perspective, the SDCS seemed to stand out as the best instrument. However, it should be modified in order to reduce floor effects on item level and thereby gain sensitivity. The Job Satisfaction Questionnaire seemed to have problems both with the construct validity and test-retest reliability. The final choice of instrument must, however, be made dependent on what one intends to measure.