Abstract: The aim of this study was to investigate whether the effect of physical activity on cognitive function in persons with dementia is moderated by patient characteristics as Apolipoprotein E and dementia type. We included 101 individuals with dementia and calculated the reliable change index to determine the change in global cognition, executive function, episodic memory, working memory, and processing speed before and after a 12-week exercise training. We found a higher treatment-related benefit in episodic memory in persons with non-Alzheimer’s disease compared to persons with Alzheimer’s disease, and in executive function in individuals with better baseline cognitive function.