The Missouri House and Senate have each passed bills that would prevent people younger than 18 from purchasing electronic cigarettes.
But the legislation passed on Thursday would also exempt those products from the state's tobacco taxes, which opponents say would allow the nicotine products to be sold with fewer restrictions.
Supporters say taxing the products would prevent the measure from passing the Republican-led Legislature. They argued that failing to pass a bill would mean children could continue buying the e-cigarettes.
E-cigarettes are battery-powered devices used to heat a liquid nicotine solution and create vapor that is inhaled.
The House voted 129-19 to send its bill to the Senate, where senators voted 27-4 in favor of their version. Both chambers must pass identical legislation by mid-May.