Designing or Planning? – Elements for a cognitive foundation of design aiding A. O. Kazakçı, A. Tsoukiàs LAMSADE - CNRS, Université Paris Dauphine 75775 Paris Cedex 16, France {kazakci,tsoukias}@lamsade.dauphine.fr Abstract This paper considers the cognitive aspects of designing. We compare these aspects to those of the (hierarchical) planning process; a process which is of common interest for Cogni- tive Psychology (CP) and Artificial Intelligence (AI). We show that both processes can be analyzed using similar key notions and they both have the same essential characteristics. Therefore, we establish a cognitive equivalence between the two processes. We discuss the implications of such an equivalence. Key words: Designing, planning, design cognition, design aiding, decision aiding.