Study aims: The purpose of this study was to determine whether youth marijuana use (past year and past month) differed based on the frequency of positive parenting behaviours. Methods: The present study performed a secondary data analysis of the 2012 National Survey on Drug Use and Health. A national sample of youth in the United States (N= 17,399) aged 12--17 years completed the survey. Findings: Results indicated 14.3% of students used marijuana in the past year while 7.8% used marijuana in the past month. Neither past year nor past month marijuana use differed based on the sex, but both did differ based on the age. Older students were more likely to have used marijuana than were younger students. Past year and past month use also differed based on the frequency of positive parenting behaviours. Students at highest risk for use were those with parents who never/seldom engaged in positive parenting behaviours. While frequency of positive parenting protected all age groups against marijuana use, the protective effect was highest for 12--13 year olds, followed by 14--15 year olds and then 16--17 year olds. Conclusions: Prevention specialists and health educators should consider these findings when developing and implementing efforts to prevent youth involvement in marijuana use.