Personalisation offers individualised treatment in circumstances where markets do not operate. Personalisation is described variously as a process involving an individualised assessment and response, the expression of individual preferences and choices, or a process in which users and professionals negotiate a common understanding of the needs of the individual. The core arguments for individualised approaches are effectiveness, efficiency and responsiveness to need. However, personalisation sometimes falls short of the claims made for it. It is not always effective, because matching people to resources is time-consuming, difficult and dependent on so many conditions that mismatches are inevitable. It may be inefficient, because it is difficult to deliver selective services without either misplaced provision or inappropriate denial of service. There is only limited support to be found for the belief that services have become more responsive to individual circumstances as a consequence of personalisation, or that they are better matched to need. The case for personalisation has to be argued and proved in the context in which it is applied.