Social comparisons are important determinants of subjective well-being. That is, subjective well-being depends not on only on one’s absolute position in terms of, for instance, status and health but also on one’s position relative to others. The present chapter provides a review of the most important literature on the relationships between social comparison processes and subjective well-being, in terms of, for example, positive affect and a positive self-image. More specifically, the identification-contrast model is used to understand how and why social comparisons may affect well-being. Special attention is paid to the role of social comparisons in times of adversity, since, in times of need, individuals often feel an enhanced need for making social comparisons. In times of difficulty and stress social comparisons may enhance feelings of well-being by providing information about how others, in similar situations, are coping and may offer reassurance if one concludes that one is better off than others. Finally, several implications of social comparison research are discussed that may help develop interventions aimed at raising individuals’ well-being.