The Benzodiazepine Dependence Self-Report Questionnaire (Bendep-SRQ) measures the severity of benzodiazepine (BZ) dependence on four domains: awareness of problematic use, preoccupation with the availability of BZ, lack of compliance with the therapeutic regimen, and withdrawal. Although promising results of the Bendep-SRQ have been obtained in cross-sectional studies, no attention has been paid to its clinical relevance during BZ withdrawal, i.e., predictive validity and time course. We performed cross-validation and evaluated the predictive validity and time course on 180 long-term BZ users who were taking part in a general practice BZ discontinuation trial. Three of the four domains had good scalability. Some concerns arose about the preoccupation scale, which emphasizes the need for cross-validation in clinically relevant populations. All scales showed excellent reliability (subject discriminability, item discriminability), while construct and discriminant validity were adequate. All four scales contributed significantly to the prediction of whether complete abstinence would be achieved directly after taking part in the discontinuation program. This prediction was independent of the other prognostic variables, except for those in the domain problematic use. The scales problematic use and preoccupation showed good sensitivity to changes during follow-up. The insensitivity of the scale, lack of compliance can be explained by low baseline scores in our population, while the insensitivity of the withdrawal scale was probably the result of the study design. In conclusion, our study indicated the clinical relevance of the Bendep-SRQ before and during a BZ discontinuation trial. We recommend the use of the Bendep-SRQ in discontinuation therapy and research into the field of BZ addiction.