The authors discuss certain important points related to a challenging problem of designing flexible heat exchanger networks (HENs). The main aim of the paper is to show the necessity of a targeting step to be employed into an overall process design of HENs under uncertainty. Such a targeting method should provide the user an insight into the complex behaviour of pinches, which depends on disturbances. Also, it should show the structural effects of pinch changes. More specifically, the following main points are discussed and analysed using examples: definitions and heuristics on convex/non-convex HEN problems and their influence on designing process; advantages and shortcomings of existing targeting methods for flexible HENs.