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Older decision-makers may capitalize on their greater experiences in financial decisions and by this offset decline in cognitive abilities. However, this pattern of results should reverse in situations that place high demands on cognitive control functions. In this study, we investigated how decision conflict affects the neural mechanisms of intertemporal decision-making in younger and older adults. To individually adjust the level of decision conflict we determined the indifference point (IDP) in intertemporal decision-making for each participant. During functional magnetic resonance imaging, participants performed choice options close to their IDP (high conflict) or far away from the IDP (low conflict). In younger adults, decision conflict leads to reduced delay discounting and lower discount rates are associated with higher working memory (WM) capacity. In older adults, high decision conflict is associated with enhanced discounting, hypoactivation in the ventral striatum as well diminished ventral striatal representations of differences in subjective values. Taken together, our results show that under enhanced decision conflict, younger adults engage in a more reflective decision mode that reflects individual differences in WM capacity. In contrast, older adults get more present-oriented under high demands on cognitive control and this decision bias is associated with changes in striatal value signaling.