The retention phase of a prospective memory (PM) task poses different challenges, including demands to store or maintain an intended action and to realize the right moment for action execution. The interplay of these processes in younger and older adults has not been explored so far. In this study, the authors examined the impact of maintenance load and task focality on PM in 84 younger and in 83 older adults. Results indicated that PM performance and ongoing task response times were strongly affected by maintenance load and age. However, a focality effect only emerged when maintenance load was low but not when attentional resources were deployed for maintaining a more demanding intention. These findings suggest that maintenance and monitoring requirements compete for similar attentional resources. Furthermore, maintenance load may affect postretrieval processes through its impact on working-memory resources, which can restrain the typical advantage of focal over nonfocal PM tasks.