This study examined the association between personality traits (i.e., anxiety sensitivity, hopelessness, sensation seeking, and impulsivity), drug use (i.e., alcohol, marijuana, and simultaneous polydrug use), and drug-related consequences in undergraduate students (e.g., academic impairment, being involved in a motor vehicle accident, and interpersonal problems). It was hypothesized that individuals who engage in simultaneous polydrug use (using alcohol and marijuana in close proximity) would have higher levels of sensation seeking and impulsivity compared to individuals who use one substance, and that simultaneous polydrug users would experience more drug-related consequences compared to individuals who use one substance. The sample consisted of 196 undergraduate students (166 females), with a mean age of 21.61 years (SD = 4.96), and the mean university level being 3rd year. Sensation seeking and impulsivity were found to significantly predict heavy episodic drinking. Sensation seeking and impulsivity were not found to have a significant relationship with polydrug or marijuana use. Within the past three years, alcohol-related consequences were significantly higher than polydrug-related consequences; marijuana-related consequences were significantly lower than alcohol-related consequences, and polydrug-related consequences were significantly lower than marijuana- related consequences. Within the past seven days, alcohol-related consequences were not significantly higher than marijuana-related consequences, alcohol-related consequences were significantly higher than polydrug-related consequences, and marijuana-related consequences were not significantly higher than polydrug-related consequences. The results from this study have the potential for substance use prevention and early intervention programs that address specific personality and drug use patterns, to be made.