Brain-damaged patients with slow mental processes may be taught compensatory strategies that might enable them to minimise disabilities and participation problems in daily life. The effects of the application of compensatory strategies should be measured in these domains of functioning. We systematically reviewed existing outcome measures used to evaluate the consequences of mental slowness. We classified measures into four categories: (1) standardised neuropsychological tests; (2) tests or questionnaires measuring general cognitive impairment; (3) measures of general everyday functioning; and (4) measures of everyday consequences of mental slowness. The majority of measures for mental slowness focus on performance in specific cognitive tasks. We found seven studies that used nine measures which focused on task-related or perceived limitations in everyday functioning. We discuss a series of reasons why measures of the perception of slowness ( including the perceived consequences of slowness) and the performance in everyday activities should be used. Such measures may be more likely to detect change or differences in performance and are certainly more relevant to patients.