This chapter provides an outline of prospective memory (PM) development from early childhood to very old age. It addresses when does PM develop/change with age? And how can these age-related changes be explained, or, in other words, what are the underlying mechanisms and processes? Preschoolers benefited from distinct compared to non-distinct PM targets, probably via the redirection of attention from the ongoing task to the PM task. The rise in PM performance during childhood is linked to the development of executive functions and to the prefrontal cortex as the involved brain structure. PM target detection is one of the processes implied in PM that has received further attention for explaining PM development during childhood. In time-based PM studies, monitoring is examined by analyzing time monitoring behavior. The influence of memory-related aspects is more rarely investigated than the role of executive functions and attentional control during childhood.