The number of Americans who work during their vacations has nearly doubled in the last decade, with the laptop computer replacing the cellular phone as the most useful tool for working on holiday.

Some 43 percent of office workers said they work on vacation, compared with 23 percent in a survey taken in 1995, said the poll conducted for Grand Rapids, Michigan-based Steelcase Inc., a designer and maker of office furniture.

Overall, roughly one in four employees said they spent three or more hours working during vacation. Most said they were committed to the job or had a pressing assignment, while 10 percent cited an inability to relax until things were taken care of.

Edward Hallowell, a psychiatrist and author of "Crazy Busy: Overstretched, Overbooked, and About to Snap!," said the trend likely includes people who keep working for good reasons as well as bad.

"The good way would be someone who says, 'Look, I really want to get away with my kids, but I do have work to do... I'm going to combine work and vacation,"' he said.

"The bad one would be someone who is just so addicted to work that they can't ever leave it. It's their only way of amusing themselves, and that's a problem," he said.

Technology, not unsurprisingly, makes all that work possible, although it has changed over the last decade.

In the latest survey, 41 percent of workers said their laptop computer made it easiest to work on holiday, followed by their cellular phone, personal computer and BlackBerry.

In 1995, most people cited their cell phone first, along with their beeper, fax machine, laptop and personal computer.

"These tools can be very freeing," Hallowell said. "They can allow you to go away, but they can also be enslaving. It's all a matter of how you use them."

The survey of 640 randomly selected full- or part-time workers was conducted in June by telephone. It was conducted by the Opinion Research Corporation.

It also found that only 61 percent of Americans use all of the vacation time they have coming to them.