The purpose of this paper is to stress the importance of selecting the right plantwide control structure and the need for a formalized approach that can encompass the many issues that arise in plantwide control design. Since the concept of process control design based on a holistic view of the process came about, the variety of procedures and approaches to the design problem have illustrated the difficulty of a unified approach. Using examples, a formal design approach is presented to help put in context the need and advantages of using such an approach. The examples deal with disturbance rejection, throughput maximization and economic optimization of plants consisting of parallel units.