This chapter concentrates on emotions in adolescence and will devote special attention to loneliness, an emotion often associated with that stage of life. Adolescents’ lonely plight cannot be discussed without reference to solitude, a notion that is related to yet distinct from loneliness. Throughout this chapter, considerable attention will be given to the interactive and socio-cultural context of emotions. It will be emphasized that emotions are typically experienced within relationships and that feelings of loneliness, for instance, can take on a different form in different types of relationship. Results of European studies on adolescent emotions and loneliness will be referred to, whenever available, and cross-cultural differences in loneliness will be discussed.