Background/Objectives: Marijuana is the most commonly used illicit substance, yet among the least studied in medication development research. Cocaine-dependent individuals frequently also use marijuana; however, little is known about the effect of this combined use on treatment presentation. Methods: Marijuana use was assessed in 1183 individuals seeking outpatient treatment for cocaine dependence. Based on past 30 days of use, the sample was divided into three groups: patients reporting no recent marijuana use (n = 634); occasional use (n = 403); and frequent concurrent marijuana use (n = 146). Differences on baseline measures of substance use, addiction severity (ASI), psychopathology, and sociodemographic characteristics were examined as a function of level of marijuana use. Results: Frequent marijuana users were more likely to be female, Caucasian, and younger than other groups. Cocaine-dependent patients with frequent marijuana use also used more cocaine and alcohol, and reported more medical, legal, and psychiatric problems, including antisocial personality disorder. Conclusion and Scientific Significance: Cocaine-dependent patients with frequent marijuana use present for treatment with more severe impairment. Accounting for this heterogeneity among participants may improve treatment outcome.