Cognitive models conceptualize attitudes and beliefs about substance use (SU) as proximal mediators of a variety of risk and protective factors for SU. Researchers have distinguished implicit and explicit cognition, but limited research has examined this distinction in the early stages of SU. The authors' goal was to examine age differences in implicit and explicit SU cognitions to clarify proximal cognitive processes that may be involved in early SU. Alcohol- and cigarette-naive children (N=76; 69.7% male; M age=11.8 years) completed the laboratory-based experiment. Likelihood ratings of costs and benefits of use assessed explicit cognitions, and a priming task assessed implicit cognitions. Regardless of age, children perceived costs of drinking alcohol and smoking as more likely than benefits. This discrepancy was smaller for older children, although this age difference was weaker for costs and benefits of cigarette use. Strong positive implicit alcohol use cognitions were apparent regardless of age. However, age differences were found for implicit cigarette use cognition. Older children were more positive about cigarette use. Findings suggest the importance of distinguishing explicit and implicit cognition for etiological models of early SU.