Illicit drug use is associated with various health problems that result in inpatient hospital admissions. The primary objective of this study was to examine all-cause and cause-specific hospitalizations by gender. The cohort comprised 4817 drug users (3365 males and 1452 females) who sought treatment in Helsinki between 1997 and 2008. Data on hospitalizations that occurred among these clients were extracted from the National Hospital Discharge Register. Crude hospitalization rates (CHRs) and standardized hospitalization ratios (SHRs) with 95% confidence intervals (CIs) were calculated, and Kaplan-Meier analysis with Log-Rank test was used to compare survival in terms of time to hospitalization between males and females. At the end of the follow-up period, 84.5% of females and 73.3% of male clients were hospitalized at least once. Female clients had higher CHR (607.6/1000 person-years, 95%CI: 594.1-621.4) than males (511.0/1000, 95% CI: 502.9-519.3), and had significantly poorer survival than males (Log-Rank test, P