The theory of planned behaviour (TPB) is one of the most widely applicable, and frequently utilised, models of human behaviour. The TPB provides a theoretical framework for assessing potential determinants of behaviour; such information can then be used to guide the creation of targeted interventions. This book provides insight on the theory of planned behaviour and its application to the field of substance use; provides information on gender variations and TPB; fruit consumption determinants among young adults in Italy; discusses moderation of intense physical activity intentions; and gives a short-communication which discusses applying the TPB on school based interventions on children's fruit and vegetable intake.