Objective: The aim was to investigate the overall amount of time spent on physical or mental activity training units (i.e., adherence) as a predictor of episodic memory performance in older healthy women. Methods: Women (N = 171, aged 70 -93 years) took part in a 6-month randomized controlled trial (physical activity or computer training, 3 times weekly). Pre-and post-intervention episodic memory and adherence were assessed. Adherence covers the objectively measured frequency of training participation including travel time to and from course sites. Results: Within the physical exercise group, adherence (β = .19, p = .03) had positive effects on cognitive performance. In the computer group, an interaction be-tween adherence and pre-intervention episodic memory (β = −.17, p = .056) indicated improvement for low-ability women. Conclusions: Adhering to a stimulating mental or physical activity intervention is a prerequisite for healthy older women to maintain or slightly improve their episodic memory performance. Travel activity should be taken into account to cover an overall stimulation. Adherence to mental activity training indicates a moderating effect of mental activity training on episodic memory. Predominantly low-ability women improve their episodic memory performance. In contrast, adherence to physical activ-ity training is positively associated with cognitive performance, regardless of pre-intervention episodic memory performance.