BackgroundThe current prevalence rate of substance abuse and dependence, represents an increasing trend of substance abuse and dependence among women, and the results of epidemiology studies indicate that substance use patterns are different between men and women. This study aimed to determine gender differences in substance use patterns and disorders among the patients undergoing methadone maintenance treatment.MethodsThis cross-sectional study was conducted throughout a specified time bracket ranging from September 2012 through March 2013 in Methadone Maintenance Treatment (MMT) clinics of Mashhad, Iran. In this study, 140 men and 120 women were selected from among the patients referring to MMT clinics in Mashhad through purposeful sampling method. The sample units were assessed using a demographic information questionnaire and Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders (SCID). The data were then analyzed by Chi Square test, Mann-Whitney U test, and Independent-samples t-test. SPSS software 16 was used to conduct statistical analyses with P values less than 0.05 regarded as significant.ResultsThe results showed that men and women are significantly different from each other in terms of marital status (p=0.001), education (p=0.001), income (p=0.001), history of injection (p=0.002), imprisonment (p=0.001), and substance use abstention (p=0.023). It was also revealed that methamphetamine dependence (p=0.017) and simultaneous use of multiple substances (p=0.001) in the past 12 months were diagnosed, to a larger extent, in male participants than those in female participants. In addition, the diagnoses of nicotine dependence (p=0.001), cannabis abuse (p=0.001), heroin dependence (p=0.001), and substance abuse and alcohol dependence (p=0.001) during a lifetime were more frequently existing in males than those in females.ConclusionThere are gender differences in substance use patterns and disorders that appear to be caused by the degree of access to substances and the impacts of cultural and social aspects on men and women in Iran.