Abstract Background: Use of alcohol and other substances is prevalent in trauma patients admitted to hospital, but little is known about the consequences substance use has on type of injury and hospital course among drug and alcohol positive trauma patients. Aims: To investigate the association type of injury and substance use had on the patient's risk of hospital admission. Further, if there was any relationship between type of substance use and type of injury. Methods: This prospective cross sectional study includes all trauma patients admitted to Ullevaal emergency department in Oslo, Norway in 2008. The patients were classified according to the International Classification of Diseases system (ICD-10) and divided in the following groups: 1.Head, 2.Neck/Thorax/Abdomen and 3.Pelvis/Extremities. Furthermore the groups were distributed on the patients’ variables: gender, age, treatment level, substance use and blood alcohol level (BAC). Results: The study includes 998 trauma patients. Of these 39,3% screened positive for substance use when admitted Trauma patients with head injury had a higher prevalence of alcohol use, 29,1%. Medicine use (mostly benzodiazepines) was more frequent in injury to pelvis/extremities, 17,3%. Multivariate analysis revealed a significant association between head injury, hazardous drug or alcohol use, and not being admitted to hospital for more than 24 hours (multivariate OR: 0,61, 95% CI: 0,41-0,93, p = 0,02). Patients with injuries to neck/thorax/abdomen and hazardous drug or alcohol use, had a higher risk of admission (multivariate OR: 5,22, 95% CI: 1,47-18,76, p = 0,01). Injuries in pelvis/extremities were more common among women who had used medicines (mostly benzodiazepines). Conclusion: 39,3 % of all patients admitted with injury screened positive for substance use, and 23,9 % screened positive for hazardous use. Of those who screened positive for hazardous use, patients with head injury had a significantly lower risk of being admitted to hospital for more than 24 hours, whereas patients with injuries to the neck/thorax/abdomen had a higher risk. Hazardous use (alcohol level = >1,0 ‰, positive screening for illicit drug use or combination use) occurred in 23,9%. Patients with injuries to pelvis/extremities were more often older women who had used medicine, mostly benzodiazepines.