This study evaluates multi-attribute utility, a modification of subjective expected utility, as a descriptive model of the adolescent's decision to initiate smoking or alcohol use. According to the model, the young decision maker envisions a set of consequences that will follow the two decision options, either to continue as a non-user or to initiate usage. Each consequence has three components. The components are the worth of the consequence, which may be positive or negative, the judged likelihood that the consequence will happen, and the importance of the consequence. Within an individual, importances will change with mood or circumstance, which is how the model accounts for impulsive decisions that may occur in social settings.