Purpose: The aim of this study was to describe the relationship between the epilepsy condition (illness severity), sociodemographic factors, general self-concept, and illness-specific attitude in adolescents with uncomplicated epilepsy. Methods: Adolescents, aged 13–22, fulfilling criteria registered in four Swedish hospitals, answered questionnaires (n=149). The instruments “I think I am” and “Sense of coherence” measured the patients’ general self-concept. The “Child Attitude Toward Illness Scale” measured illness-specific attitude. A summary score (index) calculated from seizure frequency, seizure type, and antiepileptic drug (AED) with side effects measured “Illness Severity”. Results: Illness severity was significantly related to the participants’ general self-concept, as well as to their attitude toward their condition; i.e. higher illness severity scores were correlated with lower sense of coherence (SOC), poorer self-esteem, and a more negative attitude towards the epilepsy condition. Females had more severe illness according to the Illness Severity Index, with almost 80% found in the moderate and high severity groups as compared to 63% of males in the moderate/high severity groups. Conclusions: It was concluded that the severity of the epilepsy condition was related to the adolescents’ general self-concept and illness-specific attitude, but further research is needed to understand the causality of the relationship. The brief assessment of illness severity, constructed and used in this study should be addressed and developed further.