The ability to remain mobile is an essential aspect of quality of life and is critical for the preservation of independence in old age. One of the cornerstones of comprehensive geriatric assessment is the evaluation of functional and mobility status, because it provides clinicians pivotal information on overall health status, quality of life, needs for formal and informal care, and short and long term prognosis. As a consequence, many assessment tools have been developed and proposed for clinical use, including simple self-report measures assessing basic abilities and more complex and challenging performance-based objective tools. Both self-report and objective measures might be used to investigate specific steps of the age-related disablement process. In general, self-report and performance based instruments should not be used interchangeably, since they provide different and complementary information. Selection of the more appropriate tool strongly depends on clinical setting, patient characteristics, and clinical or research objective.