Every project depends on planning, and of course a Prince2 project is no different. The process of planning is well defined in the Prince2 methodology, using the usual planning suspects of work breakdown, activity networking and scheduling. In Prince2, the method of work breakdown is the Product Breakdown Structure, essentially the same as a deliverable oriented Work Breakdown Structure, supplemented by the Product Flow Diagram (PFD). The PFD allows a high-level structure for the project plan to be agreed at the deliverable level, which could be described as a milestone-led approach. It's useful stuff, and when pragmatically integrated with your existing planning approach can deliver great benefits in the (often badly done) scope definition phase of planning.
Planning is also closely integrated with the Quality systems, with the methodology defining the production of the Product Description as a product of the process. Together, the Product Breakdown, Product Descriptions and Product Flow create an effective (and necessary!) scope definition prior to commitment of resources to the project.
Don't confuse this process with the Prince2 component 'Plans', which are a product of Planning, or 'stages', which define a Prince2 planning principle explored in the 'Controls' component.
