Prospective memory (PM) deficits are a common consequence of lesions to PFC, but their underlying neurocognitive mechanisms and processes are poorly understood. Here, we report on a patient, Z. P., who suffers from a chronic focal PM deficit, while other cognitive functions including memory are intact. His lesion involves right polar PFC (Brodmann's areas 10 and 9). Z. P. was very impaired on tasks that require detection of PM cues during an ongoing task. He was impaired regardless of whether the PM cues involved effortful or nearly effortless detection on the part of controls. By contrast, on tasks that tap the underlying (implicit) representations of intentions to perform an action, Z. P. showed normal patterns of intention superiority effects (ISEs) for to-be-performed actions and an inhibition effect for prospective actions after they had been performed. Thus, this is the first report of a neuropsychological dissociation between preserved privileged representation of prospective intentions and impaired detection of cues that support the opportune recovery of PM. Our data are compatible with the “gateway hypothesis” of rostral PFC, but also suggest there are components that are unique to PM and that remain intact after lesions to this region.