Objective: To investigate validity, test-retest reliability, sensitivity to change, and feasibility of dual task (DT) assessments in patients with dementia. Design: Validation study. Setting: Post ward-rehabilitation. Participants: Geriatric patients (n = 105) with dementia (age 82.7 +/- 5.9, MMSE score 21.9). Main outcome measures: Psychometric quality of DT performance of different DT-tests. Analyses were performed for motor and cognitive performance, and relative DT costs (DTCs). Results: Spearman's rank correlations (rs) between examined DT-tests were moderate-high for motor tasks (r(s) = 0.29-0.90), small-high for cognitive tasks (r(s) = 0.12-0.55) and small-high for relative DTCs (motor DTCs r(s) = 0.02-0.61, cognitive DTCs r(s) = -0.19 to 0.06, combined DTCs r(s) = -0.11 to 0.31). Correlations with external assessment were moderate-high for motor tasks (r(s) = 0.25-0.84), small-moderate for cognitive tasks (r(s) = -0.10 to 0.46) and small-moderate for relative DTCs (motor DTCs r(s) = -0.09 to 0.17, cognitive DTCs r(s) = -0.03 to 0.21, combined DTCs r(s) = -0.07 to 0.26). Test-retest reliability was excellent for motor tasks (ICC = 0.75-0.96), fair-excellent for cognitive tasks (ICC = 0.51-0.88) and poor-good for relative DTCs (motor DTCs ICC = 0.10-0.74, cognitive DTCs ICC = 0.05-0.65, combined DTCs ICC = 0.15-0.71). Sensitivity to change was acceptable-excellent for trained DT-tests (p <= 0.01). Effect sizes were small-large for gait parameters (SRM = 0.30-1.12), large for cognitive tasks (SRM = 0.82-0.95) and small-large for relative DTCs (motor DTCs SRM = 0.15-0.77, cognitive DTCs SRM = 0.56-0.98, combined DTCs SRM = 0.40-1.10). Completion time ranged from 13.1 to 16.9 min. Conclusions: All DT-tests showed acceptable-excellent psychometric properties in patients with dementia with highest quality for the gait-based tests 'Walking & Counting' and 'Walking & reciting ABC'. (C) 2017 Elsevier B.V. All rights reserved.