This study analyses two models (maternal and paternal) in which parental care and sources of parental knowledge moderated the relationship between parents' knowledge about their adolescents' lives and adolescents' substance use and health-related quality of life. The sample was made up of 15942 Spanish adolescents who participated in the 2006 edition of Health Behavior in School-aged Children Study. Results showed that increased parents' knowledge about their adolescents' lives reduced adolescents' substance use and increased their quality of life. With respect to the moderation relationship, a limited effect was found. However, parental care and sources of parental knowledge used by both parents generally had main effects on adolescents' substance use and health-related quality of life, with care being the most relevant variable in the health-related quality of life, while knowledge was the most relevant one for substance use.
