A planned sit-in by senior citizens at the office of Prince George's County Executive Parris Glendening yesterday turned into an orderly meeting between about 100 elderly county residents and the chief executive concerning the future use of unoccupied space at the former Camp Springs Elementary School.

The senior citizens, armed with petitions and protest signs, told Glendening that they want one unused section of the building to be a support center for the abused elderly and another to be an adult day care center. Part of the former school already houses the South County Senior Citizen Center.

"We request that you listen to us, heed us," said Eugene O'Brien, 65, who spoke for the group, Betterment for United Seniors. "These people are mad. They really are. These people are going to be right out there at the next election."

As two members of the group held up a sign that read "Seniors Vote," O'Brien warned Glendening that politicians who do not listen to the county's senior citizens "are going to be looking for new careers" after November's election.

The county is considering using unoccupied parts of the old school building for juvenile services and the Southern Maryland Vocational Training Center. O'Brien's group opposes such uses.

Glendening told the group that no final decisions have been made on how to use the remaining space at the school. He said he will look at the group's preferences "very, very carefully long before the final decisions are made," which could be in one or two months.

The South County Senior Citizen Center, at 6420 Allentown Rd. in Camp Springs, is one of five county-operated multiservice centers for the elderly operated by the county that are open five days a week. Seven other centers are open once a week. The South County center offers nutrition, health and referral services and serves as a social center for elderly residents in the Camp Springs community.

The center opened at the old Camp Springs Elementary School in late 1982 after a partial renovation of the building. O'Brien said his group thought the unused space in the building eventually would be turned over for use by senior citizens.

"We haven't been able to get from Mr. Glendening a definite statement about what he's going to do," O'Brien said in an interview. "We decided to come up here and let him know our feelings before a final decision is made. After a decision is reached, boom! Then it's too late to do anything."

The group generally was impressed that Glendening took time out to meet with them for about half an hour. But they were bothered by what he did not say.

"It's one thing for him to agree to meet with us," O'Brien said. "It'something else for him to make a decision to help the senior citizens."