In Spain, detoxification in general hospitals plays an important role in the medical care of patients. We aim to provide clinicians with information on the prevalence and correlates of psychiatric co-morbidity in drug abusers in detoxification. A sample of 115 substance-abuse inpatients (mean age 31.9 ± 6.4 years) in a Detoxification Unit of a general university hospital was studied using the Spanish version of the PRISM. Most of the patients had multiple dependence diagnoses and co-morbid axis I or axis II psychiatric disorders. Patients with dual diagnosis showed lower psychosocial functioning than patients without co-morbidity and more dependence diagnoses due to cannabis and sedatives. A total of 80% of the patients successfully completed the detoxification process. The present results enhance the value of detoxification in a general hospital as a first step of the overall treatment strategy.