This chapter discusses the process of bringing a new PICU service into being. Commissioning a new complex service can be a daunting task fraught with risks. This chapter offers a systematic guide to the thinking of service managers and others invested in service development for people with acute mental health problems. It describes the issues involved with assessing the need for a new service, understanding the population who may benefit from the PICU and bringing together the relevant stakeholders. It also examines the key components of developing a high-quality PICU service, including project management, operational policy, team development, building a unit, standard setting and service evaluation. This chapter sets out the core facets representing essential considerations for developing a new service.