This study examined the contributions of the different components of the working memory (WM) model to a range of mathematical skills in children, using measures of WM function that did not involve numerical stimuli. A sample of 148 children (78 Year 3, mean age 8 years and 1 month, and 70 Year 5 pupils, mean age 9 years and 10 months) completed WM measures and age-appropriate mathematics tests designed to assess four mathematical skills defined by the National Curriculum for England. Visuo-spatial sketchpad and central executive, but not phonological loop, scores predicted unique variance in children's curriculum-based mathematical attainment but the relative contributions of each component did not vary much across the different skills. Subsequently, the mathematics data were re-analysed using cluster analysis and new performance-related mathematics factors were derived. All three components of WM predicted unique variance in these performance-related skills, but revealed a markedly distinct pattern of associations across the two age groups. In particular, the data indicated a stronger role for the visuo-spatial sketchpad in the younger children's mathematics performance. We discuss our findings in terms of the importance of WM in the development of early mathematical ability.