The purposes of this study were to examine the therapeutic efficacy of combined group cognitive behavioral therapy (CGCBT) and to explore the characteristics of the patients who failed to complete it. Our group cognitive behavioral therapy combined with assertiveness training for alexithymia and self-esteem enhancement therapy were attended over a 10-week period. Twenty-five participants were enrolled in the study. The clinical symptoms were assessed before and after treatment, using rating scales including the Eating Disorder Inventory-2, the Bulimic Investigatory Test, Edinburgh, the Toronto Alexithymia Scale, the Rosenberg Self-Esteem Scale, and Global Assessment of Functioning. Sixteen participants (64%) completed the CGCBT program. Completion of the CGCBT resulted in significant improvements in reducing binge-eating behavior and improving social functioning. Eight patients (32%) significantly improved using the Clinical Global Impression Change (CGI-C). Stepwise logistic regression analysis of the results indicated that a lower age (P=0.04) and psychiatric comorbidity (P=0.06) were predictors of dropout from the CGCBT program. Our CGCBT program is a promising first-line treatment for bulimic outpatients. Lower age and the presence of comorbidity had effects on dropout rates.