In this article, we review three areas of research within adolescent social cognitive and affective neuroscience: (i) emotion reactivity and regulation, (ii) mentalizing and (iii) peer relations, including social rejection or acceptance as well as peer influence. The review provides a context for current contributions to the special issue of Social Cognitive and Affective Neuroscience on Adolescence, and highlights three important themes that emerge from the special issue, which are relevant to future research. First, the age of participants studied (and labels for these age groups) is a critical design consideration. We suggest that it might be logical to reduce the reliance on convenience samples of undergraduates to represent adults in psychology and cognitive neuroscience studies, since there is substantial evidence that the brain is still developing within this age range. Second, developmental researchers are broadening their scope of inquiry by testing for non-linear effects, via increased use of longitudinal strategies or much wider age ranges and larger samples. Third, there is increasing appreciation for the interrelatedness of the three areas of focus in this special issue (emotion reactivity and regulation, mentalizing, and peer relations), as well as with other areas of interest in adolescent development.