Introduction: Substance abuse is a major health problem in Bangladesh. We examined socio-demographic characteristics of male patients with substance use disorder in drug addiction treatment center in Dhaka city. Methods: This descriptive cross-sectional study was conducted in Central Drug Addiction Treatment Center (CTC), Tejgaon, Dhaka, Bangladesh from January 2012 to June 2013. Data were collected by administrating a semi-structured questionnaire comprised of socio demographic variables, family characteristics and substance related variables. A total of 136 male patients were interviewed purposively by face to face from outpatient department of CTC. Substance use disorder was established on the basis of DSM-IV TR by the Structured instrument SCID-CV (Structured Clinical Interview for DSM-IV Axis-1 Disorders- Clinical Version). Patients with comorbid psychiatric disorder and other organic brain disorders were not included in this study. Results: The mean age of 136 patients was 30.63±7.23; about 42% were in 26-30 years age group, most respondents (48.5%) were unemployed, 95% were Muslim, and 70% urban dwellers. About 85% (115) of the patients started their using drugs by cannabis, about 9% took Phensidyl as a first drug, about 59% (80) took more than one drugs. In this study, 76 out of 136 patients took drugs by smoking which constitute 55.9%, followed by injections (37.5%). Conclusions: Cannabis was the most common as the first illicit drug used by the patients. The result suggested that 18-30-year age group was most commonly abusing time. Preventive programs could be targeted on this age group.