Anaesthetists working in paediatric settings may care for patients ranging in age from preterm neonates to teenagers, some of whom will be undergoing relatively simple procedures for isolated conditions whereas others will have extremely complex needs and will be undergoing complicated, high-risk procedures. What all of these patients will have in common, however, is the need for developmentally appropriate communication from and with the professionals caring for them. Alongside an understanding and knowledge of the anatomical, physiological and pharmacological issues relevant to the care of the paediatric patient, anaesthetists also need an understanding of the developmental, communication, emotional and behavioural issues relevant to their paediatric patient. This chapter summarises some of the key theories of cognitive and psychosocial development, including beliefs about illness, and how these are relevant to the child undergoing anaesthesia. Effective communication with children and their families is central to the delivery of high-quality care, and this is discussed alongside the role of preparation and behavioural and psychological techniques in optimising experiences and outcomes for the child, family and anaesthetist.