Shifting, which is the process of switching task sets between two or more tasks, incurs a cost: participants are slower and more error prone when a switch is required, relative to when the same task is performed in a sequential manner. Recent research in our lab has found a performance dissociation between two task switching paradigms in ML, a patient with reduced short-term memory (STM) capacity. The present study investigates the hypothesis that this dissociation is a result of memory load differences between the two shifting paradigms. We tested this hypothesis by measuring shifting abilities in patients with phonological and semantic short-term memory deficits, as well as age-matched controls under standard and articulatory suppression conditions. The results suggest that task-related memory demands impair the shifting performance of patients with STM deficits, and that phonological (but not semantic) retention contributes to shifting as task requirements increase.