Abstract: Background: Military veterans are a high-risk group for health risk behaviors, including alcohol and cannabis use. However, research on veteran vs. non-veteran rates of alcohol/cannabis use are inconsistent across studies. Further, no research has investigated veteran vs. non-veteran rates of alcohol and cannabis co-use, and few studies have tested whether demographic variables, particularly race/ethnicity, moderate group differences. Therefore, the current study tested whether 1) veteran vs. non-veterans differed in rates of alcohol use, cannabis use, and alcohol and cannabis co-use, and 2) whether demographic covariates (age, sex, race/ethnicity) moderated associations. Methods: Data on adults (N = 706,897; 53.4% female) were derived from the 2002-2019 National Study on Drug Use and Health. Participant demographics, alcohol use frequency, drinking quantity, and cannabis use frequency were self-reported. Results: Non-veterans reported higher drinking quantity, cannabis frequency, and co-use. However, being a veteran was a risk factor for heavier drinking for women, ethnic/racial minoritized participants, and adults under the age of 50. Additionally, veteran status was a risk factor for cannabis use frequency in racial/ethnic minoritized participants and women. Similarly, being a veteran was a risk factor for alcohol and cannabis co-use for racial/ethnic minoritized participants, and the buffering effect of being a Veteran on co-use was reduced for older participants and women. Conclusions: Results suggest that, at the population level, non-veterans may be heavier alcohol/cannabis users. However, moderating analyses suggested that being a veteran is a risk factor for women, racial/ethnic minoritized individuals, and younger individuals. Findings are discussed in terms of public health implications.