PLAINSBORO, N.J. – State programs that provide health coverage for poor children are working, with the number of uninsured youngsters declining by more than 20 percent between 1997 and 2004, according to a new study.

Some 8 million children nationally are still without health insurance, and about 70 percent of them are eligible for coverage, the researchers said.

Maine was among the leaders in reducing the number of uninsured youngsters, according to the report. Maine reduced the number by 50.1 percent, from 34,274 to 16,881, during the period. Only Arkansas was better, at 59.9 percent.

The study was released Wednesday by the Robert Wood Johnson Foundation, a Plainsboro health advocacy organization. The analysis was compiled from census figures by the State Health Data Assistance Center at the University of Minnesota.

The foundation credited the State Children’s Health Insurance Program, which uses a mix of state and federal dollars to pay for insurance. Every state has some version of the program, launched in 1997.

“It has shown that it can be successful and it is a very important safety net for kids who are not covered,” said Elaine Arkin, a spokeswoman for the foundation.