AbstractThis chapter introduces the three words of the title: vacation decision making (DM). First, the major paradigms used to investigate DM is presented, both general and consumer-specific theories are discussed. Second, the major variables influencing the vacationer's DM process (DMP) are briefly described by outlining three categories: (i) socio-psychological processes (perception and information processing, learning, attitude formation and change); (ii) personal variables (motivation and involvement, personality and self-concept, values and lifestyles, emotions); and (iii) environmental variables (socio-cultural, interpersonal and situational). Third, vacation and tourism are made unambiguous concepts, by introducing both in a socio-anthropological perspective (i.e. the phenomenon) and in economic terms (i.e. the product).