The study examined the effects of attachment attitudes, social support, and psychological and behavioral problems on pathological gambling among adolescents. Method: A total of 268 male adolescents from 15 to 17 years of age (M = 16.23, SD = .39) completed self-report measures on gambling behaviors, attachment styles, social support, and internalizing and externalizing problems. Results and Conclusions: At-risk and pathological gamblers reported lower level of social support and higher level of fearful attachment and internalizing problems than non-problematic gamblers. Results from a discriminant function analysis, in which two discriminant functions emerged, were consistent with contemporary perspectives on personality functioning: in fact, it resulted that the difference between non-gamblers and at-risk gamblers was better explained by a function named "self-in-relation", which included internalizing problems, fearful attachment, lack of security and low perceived support, whereas the difference between at-risk gamblers and pathological gamblers was better explained by a function named "self-definition", which included externalizing problems and preoccupied attachment. Therefore, findings of this study suggest that more severe gambling behaviors in adolescence are associated with needs for self-definition. This can have important implications for the assessment and treatment of adolescent gamblers.