Assembly automation in form of robotized assembly cells is one of the most important application areas of robotics today and in the future. The flexibility of these cells offers possibilities to automatize assembling of small and medium lots. Planning of assembly cells will be done manually in most cases by means of some computer facilities. The paper presents first results for totally computer aided planning. The creation of an integrated database model, the planning process and knowledge will be discussed. The assembly operations, their sequencing, list of selecting components, assembly time and price of flexible cells are the goals of the proposed planning system.