Background: Everyday technologies (ET) such as smart phones, and internet banking are increasingly incorporated into daily activities. Therefore, valid assessments are needed to identify ability in ET use and to design and evaluate interventions. Aims: To evaluate and compare the stability over time (test-retest reliability) of measures generated with the short version of the Everyday Technology Use Questionnaire (S-ETUQ) in older adults with cognitive impairment or mild dementia. Materials and Methods: Data was collected with S-ETUQ at two occasions (m = 20.9 days in between) in a sample of (n = 73) older adults with cognitive impairment of different origin (n = 38) or mild dementia (n = 35). Stability of each participant’s S-ETUQ measure was examined using standardised difference z-comparisons. The test-retest reliability coefficient of the S-ETUQ measures was determined by Intraclass Correlation Coefficients. Comparisons were performed using Mann-Whitney u-tests. Results: The S-ETUQ measures were statistically stable between the two occasions. Hence, the group of persons with cognitive impairment demonstrated slightly higher stability and fewer differences compared to the group with mild dementia. The ICCs (0.82–0.90) indicated good to excellent agreement. Conclusions: S- ETUQ can be used with older people with cognitive impairments of varying degree to gather reliable and precise information regarding their use of ET.