Younger adults' decision-making behavior is often a combination of model-free (MF) and model-based (MB) decision strategies. In contrast, older adults seem to primarily rely on MF strategies. This age-related shift in decision strategies has been interpreted in terms of a deficit in the representation of transition structures necessary for MB decision-making. The aims of the current study were twofold. First, examine if the degree of MB decision-making in older adults is sensitive to changes in the demands on representing the transition structure, and second, the neural dynamics underlying age-realated shifts in decision strategies.