BACKGROUND: Spatial orientation is required for independent mobility in society. Deficits in spatial orientation can be an early symptom of Alzheimer's disease and other dementias, and there is a need for brief assessment tools to identify impairments. OBJECTIVE: The aim of this study was to evaluate the construct and known-group validity of our newly developed Spatial Orientation Screening (SOS) questionnaire. METHODS: We included 132 patients with subjective cognitive decline (n = 16), mild cognitive impairment (n = 32), or all-cause dementia (n = 84) from a memory clinic and a reference group of cognitively unimpaired older adults (n = 108). The patients and their next-of-kin answered the self- and proxy-rated versions of the 4-item SOS (0-8 points) and the 10-item Questionnaire of Everyday Navigational Ability (QuENA, 0-30 points). The patients also performed the Floor Maze Test (FMT) for performance-based spatial abilities. RESULTS: Mean ages (SD) of the patient and reference groups were 68.6 (±7.6) years and 73.7 (±6.7) years, respectively. Construct validity between self-rated versions of the SOS and QuENA was satisfactory with r CONCLUSIONS: The SOS had satisfactory validity for use as a screening instrument for assessment of spatial orientation in memory clinic patients.