Electronic cigarettes are battery-powered devices that provide users with aerosol puffs that typically contain nicotine, and sometimes flavorings like fruit, mint or chocolate. They've often been described as a less dangerous alternative to regular cigarettes.
Unlike regular cigarettes, the federal government does not regulate e-cigarettes, although about 20 states have banned store sales to minors.
The new study released Thursday by the Centers for Disease Control and Prevention is based on a questionnaire filled out by nearly 19,000 students in 2011 and another 25,000 in 2012.
In 2011, about 3 percent said they'd tried an e-cigarette at least once. That rose to 7 percent last year and translates to nearly 1.8 million students.
In contrast, 6 percent of adults have tried e-cigarettes, according to a different CDC survey done in 2011.
Children still are more likely to light up regular cigarettes, though teen smoking rates have dropped in the past decade. More teens now smoke marijuana than tobacco, surveys have found.
Some makers of e-cigarettes said Thursday that they supported regulations that keep the devices out of kids' hands. But some are wary of steps that might affect adult buyers.
Future regulations shouldn't "stifle what may be the most significant harm reduction opportunity that has ever been made available to smokers," Murray Kessler, chief executive of Lorillard Inc., the nation's third-biggest tobacco company and owner of Blu Ecigs, said in a statement.