OBJECTIVE: Internet-based guided self-help (GSH) programs increase accessibility and utilization of evidence-based treatments in binge-eating disorder (BED). We evaluated acceptance and short as well as long-term efficacy of our 8-session internet-based GSH program in a randomized clinical trial with an immediate treatment group, and two waitlist control groups, which differed with respect to whether patients received positive expectation induction during waiting or not. METHOD: Sixty-three patients (87% female, mean age 37.2 years) followed the eight-session guided cognitive-behavioural internet-based program and three booster sessions in a randomized clinical trial design including an immediate treatment and two waitlist control conditions. Outcomes were treatment acceptance, number of weekly binge-eating episodes, eating disorder pathology, depressiveness, and level of psychosocial functioning. RESULTS: Treatment satisfaction was high, even though 27% of all patients dropped out during the active treatment and 9.5% during the follow-up period of 6 months. The treatment, in contrast to the waiting conditions, led to a significant reduction of weekly binge-eating episodes from 3.4 to 1.7 with no apparent rebound effect during follow-up. All other outcomes improved as well during active treatment. Email-based positive expectation induction during waiting period prior to the treatment did not have an additional beneficial effect on the temporal course and thus treatment success, of binge episodes in this study. CONCLUSION: This short internet-based program was clearly accepted and highly effective regarding core features of BED. Dropout rates were higher in the active and lower in the follow-up period. Positive expectations did not have an impact on treatment effects.