The present study looked at prospective memory development between 7-15 years of age (N=57). Past research has draw no coherent picture of prospective memory development due to variations in prospective memory tasks employed, motivation not being suppressed, time-based and event-based memory not being distinguished and time delay between intention formation and intention execution not being controlled. The present study aimed to overcome these issues and draw a more coherent picture of prospective memory development. To investigate event-based prospective memory participants were asked to name pictures on slides (ongoing task) whilst remembering to do something when they saw a target animal slide (prospective memory measure). To test time-based prospective memory it was noted whether participants remembered to bring back consent forms (after 1 week) and take a letter at the end of the experiment (15 minute delay). The results showed that event-based prospective memory did show improvement, reaching asymptote at 8 years of age. Time-based prospective memory also showed improvement, but continued to improve past 8 years of age. An effect of time delay on performance was found with children performing better on prospective memory tasks when delay interval was shorter. Additional findings concerned no gender differences and no relationship between prospective memory and retrospective memory. The present study managed to overcome problems of previous research, providing a more coherent picture of prospective memory development in childhood and adolescence, and accentuated the importance of not using prospective memory as an umbrella term for event-based and time-based memory as well as the importance of controlling time delay and motivation.