Some nonprofit organizations that traditionally have offered help to the poor and desperate in times of need are now poor and desperate themselves.

Because of the state of the economy, the leaders of these groups say there is less money to go around and less time for people to volunteer. As a result, more people are suffering. And since President Reagan's economic proposals were passed in Congress last year, social service agencies--both those funded by the federal government and by the private sector--have been preparing for the major financial blow they expect sooner or later, even as requests for such services are increasing.

Soup kitchens have longer lines outside their doors. Shelters for street people are full every night, and church organizations that provide emergency services are being stretched to their limits.

Some organizations are coping well with this increase in demands from their needy clients, but others aren't so fortunate. For the most part, groups in the District are more hard-pressed than their suburban counterparts.

Some on the hard-pressed list:

Southeast Neighborhood House is being forced to trim its programs just as demand has increased.

Southeast House operates a number of programs for the United Planning Organization, including a geriatric day care center, a senior recreation center, six nutrition sites, a developmental youth day care center and a juvenile diversion program.

This year, UPO slashed the Southeast House's funding by nearly one-third from $258,000 to $169,000.

As a result of the budget cuts, six certified housing counselors, two community education specialists and an emergency services specialist were fired and the entire housing department was abolished.

Because the Reagan administration has wiped out the Comprehensive Employment and Training Act program, Southeast House's youth services staff was reduced from 18 to four and its Manpower youth employment program was terminated. That program employed 93 teen-agers last year.

Sasha Bruce Youth Work Inc. operates a shelter for runaway teen-agers, a program offering an alternative to detention of juvenile defendants, a group home for girls and one for boys, and an outreach project for home and job counseling.

Cuts in social programs have caused Sasha Bruce to lose $120,000 in funding this year, said Deborah Shore, its executive director. "This terrific decrease in funding has put us into an emergency situation where we've had to go to everyone for help."

If financing disappears, Sasha Bruce will close its doors. "It is a totally unrealistic plan to expect the private sector to pick up where the government left off," Shore said. "For the most part, corporations and individuals are not helping us."

* At the House of Ruth, Executive Director Jamie Goldberg says the number of persons seeking help has increased "drastically."

The House of Ruth includes a home for battered women and a shelter for homeless women in Northwest. Goldberg attributed the increases to major cuts in social programs, the "deinstitutionalization" movement and a serious low- to moderate-income housing shortage in the District.

"There is a crying need for an increase in services to the needy," Goldberg said. "I find it personally offensive that the government doesn't seem to care."

The District government picks up the tab for about 80 percent of the House of Ruth women's shelter operating costs--$263,520 this year. The rest is raised by cash contributions and profits from a thrift store that it runs to help make ends meet.

House of Ruth's home for battered women is funded completely by private donations and, according to board member Mary Sears, that's where the House of Ruth is really hurting.

"People are demanding more and they really need more, and we have to try to help them," Sears said. "We can't turn them away."

* Focus (Fairfax Organization of Christians and Jews United in Service) hasn't turned away anyone needing help, either. But Mary Michaud, emergency committee coordinator for Focus, says, "It's really a little bit early for us to see" just how hard Reaganomics will hit the organization.

The group, which gets about half its funding from 20 church congregations in Fairfax County and the other half from individuals, runs a program to help needy families meet utility bills, pay rent and buy food and medicine. It also runs a food pantry, a clothing center, a furniture center, a housing rehabilitation program and a meals-on-wheels program.

Michaud said Focus is getting more calls from people who have "unreal expectations" about what Focus can provide. The group has limited itself to providing up to $250 per month per family. Its budget allows a monthly expenditure of about $1,500.

When the organization formed in the late 1960s, several hundred people (mostly women with young children) answered telephone calls from needy families in the Fairfax area. Now, there are only two women who answer phone calls.

Some organizations have fared better, however.

Workers in Alive (Alexandrians Involved Ecumenically) are increasing their activities. The consortium of 30 religious congregations delivers food, pays rent, utility bills, medical bills and transportation costs, and transports furniture to families who need the help.

It also runs an emergency shelter for families and women who are alone, sponsors a federal program for retired senior volunteers, and operates a day care center for children of working parents that operates on a sliding fee scale.

In addition to these projects, Alive coordinators decided recently to take on small projects that the federal government has dropped.

At Zaccheus Soup Kitchen at 612 L St. NW, the generosity of volunteers is also showing. The kitchen is in a rundown section of the District and is operated by Catholic Workers. It dishes out about 300 bowls of soup a day.

Gloria Grover, a volunteer at Zaccheus for four years, feels the kitchen will survive whatever economic crisis lurks in the future because it has survived past economic downturns since its opening in 1971.

Why are some nonprofit organizations thriving while others are faltering?

For one, there is a relative difference between groups based in the suburbs and those in the District. The average income level of suburban donors is higher than the level for inner-city dwellers, so cash contributions to suburban groups tend to be greater, group leaders said.

Another reason is the groups are in need of different kinds of help. For example, Laplois Ashford, director of Southeast House, said it has enough volunteers to keep it going, but it needs more money to hire supervisors.

"If you're going to use volunteers, you must have the basic staff resources to keep the place going," Ashford said. "Staff supervision is essential, but we don't have the money to hire more staff."