Self-concept may be defined as the totality of perceptions that each person has of themselves, and this self identity plays an important role in the psychological functioning of everyone. To date, however, there has been no investigation into the relationship that physical self-concept has with psychological well-being or psychological unwellness. The author of the thesis is Ms Arantzazu Rodríguez Fernández, who presented her work under the title, (Physical self-concept and psychological well-being/unwellness during adolescence). Ms Rodríguez is a graduate in Psychology and carried out her PhD under the direction of doctors Alfredo Goñi Grandmontagne and Igor Esnaola Etxaniz, of the Department of Evolutionary Psychology and the University School of Education at the UPV/EHU. She currently works as a research worker at the university. This research had three fundamental objectives: to study the relationship between physical self-concept and psychological well-being, to identify the relationship between physical self-concept and anxiety and depression and, finally, to analyse the relationship between physical self-concept and Eating Behaviour Disorders (EBDs) — amongst both the non-clinical population in general as well as amongst patients previously diagnosed with anorexia or bulimia nerviosa. To undertake the research, a total of 1,959 young people between the ages of 12 and 23 from the Basque Country, Burgos and Rioja were studied. 48 of these were patients diagnosed with some form of EBD. The data obtained indicated that physical self-concept is related in a positive manner with the psychological well-being of the individual and in a negative manner to psychological unwellness, in such a way that the more one is happy with one’s physique, the more psychological well-being one has, with less levels of anxiety and depression and less risk of suffering from an EBD. This relationships have also been analysed as a function of age, gender and physical activity. As a general rule, it is seen that, taking into account physical self identity, male adolescents present higher scoring for psychological well-being than their female peers. This same relationship is established between12-14 year old adolescents on the one hand and 15+ adolescents on the other, and between those who do physical activity and those who do not. But, considering all the variables at the same time, it was seen that adolescents with more positive physical self-concept and who are, at the same time, between 12 and 14 or carry out physical activity, score higher for psychological well-being, without any significant difference between the sexes being observed. This research also showed young people experienced psychological unwellness in relation to their physical appearance throughout their adolescence, whether their perception of their physique is low, average or high. Nevertheless, undertaking sporting activity appears to be a good way to minimise any psychological unwellness, probably because it enhances physical self-concept. It is only when physical self-concept is low that doing physical exercise gives rise to the potential risk of suffering EBD. As a rule, however, sport can be defended as a way of increasing personal well-being and reducing psychological unwellness. As regards disorders associated with physical appearance, the greatest risk of developing an anxiety disorder is after the age of 15; for a depressive disorder the risk stage is between 12 and 17; and for anorexia or bulimia nerviosa the risk period is between 18 and 23. Finally, of all the elements conditioning physical self-concept, the outstanding one is that of an attractive physical appearance, because the self-perception of this is strongly related to anxiety, depression and psychological well-being. All this, of course, is a reflection of how society favours relationships between what is attractive as perceived by one and how anxious, how depressed or how happy one feels with oneself.