Personality traits are important individual characteristics modifying responses to therapy in various diseases. The aim of this study was to identify personality traits that may predict treatment outcome in alcohol-dependent patients. The present analysis was based on a total of 146 alcohol-dependent patients (109 male, 37 female) after detoxification. The variable of interest was treatment outcome (abstinence/relapse) after a 1-year follow-up. To identify personality traits as predictors of treatment outcome, 5 personality questionnaires (NEO 5-Factor Inventory, Temperament and Character Inventory, Eysenck Personality Questionnaire, Eysenck Impulsiveness-Venturesomeness-Empathy Scale and Sensation-Seeking Scale) were applied. Data analysis was performed by using a classification and regression tree analysis (CART; a nonparametric technique for data with a complex structure) in order to find a decision rule to predict treatment outcome from personality traits. The CART model identified psychoticism and persistence as the 2 most relevant discriminatory parameters, of which psychoticism was used as the first node in the model, classifying 64% of the patients correctly as relapsed and 12% correctly as abstinent. In addition, the risk of relapse was even higher in patients with a substantial score in psychoticism and a low score in persistence. When comparing relapsed and abstinent patients, further variables, such as scores for novelty seeking (20.9 ± 5.5 vs. 18.5 ± 5.9) and impulsiveness (8.4 ± 3 vs. 7.2 ± 3.5), showed significance. In addition, relapsed patients lived alone more often than abstinent patients (52 vs. 25%, p = 0.004). In conclusion, this analysis demonstrated that specific personality characteristics, namely psychoticism and persistence, are usable predictors for the risk of relapse in alcohol-dependent patients.