36 Chapter 3 Abstract Background: The party drug Gamma hydroxybutyrate (GHB) is highly addictive. GHB use disorder (GUD) has poor treatment outcome, with relapse rates over 60% within three months after detoxification. In order to get a better understanding of the limited treatment success, we explored GUD patients’ illness perceptions and treatment needs. Methods: In a qualitative cross-sectional observational study, using a semi-structured interview based on the works of Kleinmann, illness perceptions were explored among treatment seeking GUD patients (n=20). The analysis was based on the principles of Grounded Theory by the two interviewers and an independent researcher. Results: GUD patients had mainly positive views towards GHB. GHB was perceived as strongly rewarding and perceived as the solution to psychosocial problems, rather than the cause. After repeated re-admissions GUD patients perceived themselves as addicted to GHB and GHB use as more problematic. They reported a need for personalized treatment goals, which were mainly aimed towards dealing with psychiatric symptoms and social reintegration. Conclusion : GUD shares many characteristics with other substance use disorders, in line with gradual development from positive reinforcement in early stage GUD to negative reinforcement in later stages of more compulsive GHB use. Future studies should investigate whether personalization of treatment goals, like social reintegration, lead to better treatment outcomes.