Purpose: This study explored the oral health of individuals with substance use disorders and examined the relationship between oral health and type and number of years of substance use disorder. Materials and Methods: This comparative cross-sectional study comprised patients with one of four groups of substance use disorders – alcohol, cannabis, central nervous system stimulants (CNSS), and opiates. All participants underwent a dental examination and were included in the study based on their clinical findings. Results: Of 95 participants, 79 (83%) were male and 37 (39%) were homeless. Statistically significant difference between the groups was observed in 6–12-mm periodontal pocket depths (p <0.05), as were differences in oral mucosal changes (p <0.001). Statistically significantly lower proportions were observed in the cannabis group for Mob G:0 and Mob G:1 and Furcation G:1 compared to the CNSS and opiate groups; the proportion of Furcation G:0 was significantly lower in the alcohol group compared to the cannabis group. Analysis of variance (ANOVA) revealed statistically significant between-group differences in age, number of years of substance use disorder, number of teeth, and decayed, missing and filled teeth (DMFT). When controlling for age and gender, substance type was found to be a statistically significant predictor of number of teeth (B = –4.4; 95% CI: –8.1 to -0.38; p = 0.03) and DMFT (B = 2.1; 95% CI: 0.86 to 3.3; p = 0.001). Conclusions: These results indicate poor oral health among individuals with substance use disorders. It seems that oral health problems are lower among abusers of cannabis than of CNSS, alcohol and opiates.