Method: National cross-sectional multi-ethnic annual survey (2002-2004 combined) of 91,219 Year 10 students aged 14 and 15 years (46,400 girls, 44,819 boys; 59,983 Europeans, 16,471 Maori, 8400 Asians, 6365 Pacific Islanders) who answered an anonymous self-administered questionnaire.

Results: Maternal smoking and paternal smoking were associated separately with increased risk of daily adolescent smoking in all ethnic groups except paternal smoking in Asian youth. The relative risk of adolescent daily smoking (adjusted for age and sex) was significantly higher for maternal only smoking compared with paternal only smoking in each ethnic group: Asians 5.50 (95% CI: 3.55, 8.52), Europeans 1.38 (1.26, 1.52), Pacific Islanders 1.38 (1.10, 1.73), and Maori 1.10 (1.00, 1.21). The net effects of maternal and parental smoking were additive among European, Maori and Pacific Island students, but multiplicative in Asian. Gender-specific effects were not consistent, with maternal smoking being stronger in girls than boys only among Maori and European students; while the absolute effect of paternal smoking was the same for boys and girls in all ethnic groups. Overall, 43% of female adolescent daily smokers, and 41% of male, could be attributed to parental smoking.

Conclusions: Parental smoking is a consistent risk factor for adolescent smoking in all ethnic groups.

Implications: Prevention strategies targeted at parents have the potential to limit the uptake of smoking by adolescents.