Background: Monocentric studies of inpatient opiate detoxification treatment show considerable variability regarding treatment success rates. This multicentric study investigates whether patient characteristics explain the different rates of regular discharge between treatment units. Methods: 1,017 opiate-dependent patients from 12 detoxification units with similar treatment programs, funding, staffing and equipment were analyzed. Patient data and outcomes were documented by treatment staff using a standard form. Results: Controlling for center, regular discharge (range: 14–49% between centers) was significantly associated with pre-existing plans for follow-up treatment, previous completed long-term residential and detoxification treatments, fewer unsuccessful detoxification treatments, higher age, later onset of opiate use, and longer duration of use. Controlling for patient characteristics, the center variable was significantly associated with outcome in a multiple logistic regression analysis. Conclusions: Regular discharge could best be predicted by patients’ plans for follow-up treatment and previous treatment outcomes. Although treatment units had equivalent resources and regulations, and although patient effects were statistically controlled for, there were still considerable center effects. Setting factors as well as actual drop-out processes should be investigated more closely in the future.