Working memory is often described as a system for simultaneous storage and processing. Much research -and most measures of working-memory capacity -focus on the storage component only, that is, people's ability to recall or recognize items after short retention intervals. The mechanisms of processing information are studied in a separate research tradition, concerned with the selection and control of actions in simple choice situations, dual-task constellations, or task-switching setups. both research traditions investigate performance based on representations that are temporarily maintained in an active, highly accessible state, and constrained by capacity limits. In this article an integrated theoretical framework of declarative and procedural working memory is presented that relates the two domains of research to each other. Declarative working memory is proposed to hold representations available for processing (including recall and recognition), whereas procedural working memory holds representations that control processing (i.e., task sets, stimulus-response mappings, and executive control settings). The framework motivates two hypotheses: Declarative and procedural working memory have separate capacity limits, and they operate by analogous principles. The framework also suggests a new characterization of executive functions as the subset of processes governed by procedural working memory that has as its output a change in the conditions of operation of the working-memory system. Throughout his career, andre Vandierendonck has worked on a better understanding of the limits of human cognitive capacity. among other things, he has a long-standing interest in the operating principles of working memory and of executive functions. both concepts play an important role in determining the success of our cognitive endeavours. The concept of working memory derives from the older concept of a short-term memory store, and due to this heritage, working memory is often described as a system for the shortterm storage and processing of information. both the storage capacity and the processing capacity of working memory are thought to be limited. The limited storage capacity is most apparent when people are asked to remember new sets of items (e.g., lists of words, arrays of objects) that are briefly presented to them for immediate recall or recognition. accuracy in such tasks declines sharply as the set size of memory items increases, leading some researchers to estimate the storage capacity of working memory to about four items (Luck & Vogel, 1997;Cowan, 2001). The processing capacity of working memory is more difficult to grasp, and has therefore attracted less systematic research. Inspired by the work of baddeley (1986), the processing