Two local lawmakers on the committee were split over the issue.
Del. Louise V. Snodgrass, R-Frederick/Washington, said parents should have a choice about whether to use booster seats.
To mandate booster seats burdens families, especially the working poor who would lose income to fight the charge in court, she said.
"I don't think that's fair. We're not giving parents enough credit. Anyone who has children wants to do the best for their children," she said.
Del. Christopher B. Shank, R-Washington, said he was skeptical at first about creating more government interference in people's lives. But he was persuaded by parents who told him their young children were killed in car accidents because a simple seat belt didn't save them.
"It was so horrible and so emotional to see," he said. Those parents trusted the state to set proper safety standards, he said.
Only 5 percent of children between the ages of 4 and 8 in Maryland ride in booster seats, according to the bill's sponsor, Del. Bill Bronrott, D-Montgomery.
"Most parents in Maryland are currently playing by the rules as they are currently written. But the rules of the road are flawed," he said.
Seat belts aren't designed to prevent small children from being hurt in car crashes, he said.
Backers of the bill include the National Transportation Safety Board, the American Academy of Pediatrics, American College of Emergency Physicians, U.S. Department of Transportation, Maryland Institute for Emergency Medical Services Systems, Maryland State Police and Johns Hopkins University.
Parents who don't comply would be subject to a $25 fine plus court costs, which a judge can waive if the parent buys a booster seat.
A booster seat costs about $48, Bronrott said.
In the Senate, Sen. Donald F. Munson, R-Washington, and Sen. Alex X. Mooney, R-Frederick/Washington, both voted to approve the booster seat law.
Mooney said he's generally against putting too many restrictions on people and gave a speech to that effect on the Senate floor Thursday.
Speaking against a bill to require helmets for children riding in-line skates and scooters, Mooney said, "Why don't we mandate helmets for walking up and down the stairs. It's getting ridiculous. We can't mandate common sense."
The Senate gave the helmet law, which would apply to anyone 16 and under, preliminary approval Thursday.