This study investigated the effect of individual differences in state anxiety on tasks tapping the central executive, phonological, and visuo-spatial components of working memory (WM). It was designed to test Eysenck and Calvo's processing efficiency theory (PET) which suggests that the phonological and executive components of WM may be important in understanding learning outcomes in anxiety. Typically-developing children aged 9-10 years were split into high and low state anxiety groups. They performed three WM tasks--forward and backward digit span (assumed to measure phonological and central executive components of WM respectively) and a spatial working memory task (measuring the visuo-spatial component of WM). Measurements of task accuracy were taken as an indicator of performance outcome or effectiveness. Time taken to complete tasks and a subjective rating of mental effort were taken as measurements of performance efficiency. No differences were found between high and low state anxiety groups in task accuracy for any measure. Children in the high state anxiety group, however, took longer to complete the backward digit span task and reported increased mental effort in the forward digit span task, indicating some effect of anxiety on measures of performance efficiency.