Working memory (WM) improves dramatically during childhood but what drives this improvement is not well understood. One influential account thus far has proposed a simple increase in storage capacity. However, recent findings have shown that multiple factors, such as differences in the ability to use attention to enhance the maintenance of internal representations, as well as changes in WM precision, also interact in influencing age-related differences in WM capacity. We aimed to examine whether and how the developing ability to orient attention retrospectively to internal representations influences WM precision. To do so, we employed a paradigm that combined the continuous-recall WM task with the partial-cueing report task. Specifically, 7-year-olds and young adults were asked to reproduce the colour of a probe item in a colour wheel. The initial memory array, which included the probe item, could be followed by a spatial cue that directed participants' attention to a location in the memory array (a 'retro-cue'). Results showed that attentional biases engendered by retro-cues facilitated overall precision compared to uncued baseline performance, for both age groups, although to a smaller degree in 7-year-olds compared to adults. Importantly, investigation of modelling parameters suggested that children demonstrate lower representational quality of items in WM but that spatial attentional cues improve overall precision by increasing the probability of target storage, maintenance and recall, and by reducing misbinding errors as well as random guessing, not by changing representational quality. These results add significantly to our knowledge on the relation between retrospective attention and WM development.