Background:
Many non-smokers die annually as a result of exposure to second hand smoke. School going adolescents are often understudied but may be at increased risk.

Methods:
A descriptive cross-sectional study was carried out among 353 students in four schools in Ajeromi Ifelodun an urban district in Lagos state, using a multi-stage sampling technique. Data was collected using a self administered questionnaire adapted from the global youth tobacco survey and analysed using Epi Info version 7.

Results:
Of the respondents 51.8% were males and 48.2% females, their ages ranged from 12-20 years. More than half of the respondents (54.4%) had good knowledge of the associated health risks of second hand smoke exposure. Majority were in favour of banning smoking in restaurants (64.6%), clubs (64%), and outdoor public places (62.6%). Overall, 23.8% were exposed to second hand smoke at home, while 64.6% and 71.1% were exposed to second hand smoke in enclosed and outdoor public places respectively.

Conclusions:
Despite the passage of national and state wide anti smoking laws, the level of exposure of these students to second hand smoke was still high particularly in public places. This highlights the need for urgent efforts to enforce smoke free policies to protect young people from second hand smoke exposure.