Aims: To test the hypotheses that average volume of alcohol consumption and patterns of drinking, each influence alcohol-related problems and that both act at individual and aggregate levels. Methods: The 2003 cycle of the Ontario Student Drug Use Survey obtained self-administered questionnaires from a representative classroom-based survey of 2455 Ontario secondary school students (grades 9–12) from 74 schools, with a student completion rate of 72%. Average volume of alcohol consumption was assessed using a quantity-frequency measure. Heavy drinking occasions were operationalized by four dummy variables indicating less than monthly, monthly, weekly and daily consumption of five or more drinks per occasion, with never having a heavy drinking occasion serving as the reference group. Alcohol-related problems were measured by using seven items of the Alcohol Use Disorders Identification Test. Results: As hypothesized, both the average volume of alcohol consumption and patterns of drinking influenced alcohol-related problems at the student level, independently of each other. At the school level, both determinants significantly influenced the problems, but not when simultaneously entered into the equation. Conclusions: Future prevention of alcohol-related problems in adolescents should consider both the average volume and patterns of drinking. Both prevention and research should also try to include environmental determination of alcohol-related problems.