Correlations between various classes of working memory tasks (working memory span tasks, updating tasks) were analyzed. Tasks that share processing and storage requirements correlated with each other. A three factor structure was extracted compatible with the existence of three components within working memory: focus of attention, region of direct access, and activated memory. The data shows that processing and storage are independent in working memory and that storage in working memory is based on two storage systems — one that uses short-term memory mechanisms and one that uses long-term memory mechanisms.