Objective. We assessed changes in levels of support for smoke-free bars and restaurants among teens and young adults before and after implementation of a statewide smoke-free law. Methods. We measured support for smoke-free bars and restaurants among teens and young adults aged 16-24 years living in Minnesota (n52,785) and five comparison states (n5404), up to 12 months before and up to six months after Minnesota's smoke-free law went into effect in October 2007. We compared changes in support among three subgroups-Minnesota participants who lived with a previous local smoke-free law, Minnesota participants who did not live with a previous local smoke-free law, and participants from the comparison states-before and after Minnesota's statewide smoke-free law went into effect. Results. Support for smoke-free restaurants and bars among participants in Minnesota and comparison states increased after Minnesota's smoke-free law went into effect. Minnesotans, both those living with and without a previous local smoke-free law, showed similar increases in support for smoke-free restaurants as participants in comparison states. However, Minnesotans living without a previous local law showed larger increases in support for smoke-free bars than both those in comparison states and those living in Minnesota with a previous local smoke-free law. Conclusions. Our study employed a more robust design than similar studies and focused on the teen and young adult population. Our results will help advocates and policy makers demonstrate how public support for smoke-free laws increases following smoke-free legislation, particularly among those who were not previously living with a local smoke-free law.