Objectives: This study examined the relationship between psychiatric symptoms and nicotine, caffeine, alcohol, and marijuana use in young adult smokers. Methods: Young adult smokers completed self-report measures of nicotine, caffeine, alcohol and marijuana use, Conner's Adult Attention-Deficit/Hyperactivity Disorder Rating Scale-Short Version (CAARS-SS), beck depression inventory (BDI) and beck anxiety inventory (BAI), and provided a breath carbon monoxide sample. Results: Self-reported cigarette use was positively correlated with carbon monoxide, CAARS-SS, and BDI levels. Caffeine intake was correlated with CAARS-SS, BAI, and BDI levels and emerged as the more significant predictor of BDI, BAI, and CAARS-SS scores when regressed with cigarette use. Conclusions: Caffeine use is associated with psychiatric symptoms in young adult cigarette smokers and should be considered in future research.