Working memory (WM) has been associated with the acquisition of arithmetic skills, however, the components of WM that underlie this acquisition have not been explored. This study explored the contribution of two WM systems (the phonological loop and the central executive) to mathematical performance in young children. The results showed that a two-factor structure separating short-term memory (STM) and WM tasks predicted individual differences in mathematical performance. WM was independent of the contribution of STM and naming speed in predicting children's mathematical performance. However, these basic capacities correlated substantially with the math performance factor, and jointly accounted for over 74% of the Math Performance factor. The results were interpreted as support for the notion that both the central executive system (controlled attention) and storage system of WM predict children's math performance.