The Community Foundation of Greater Washington yesterday announced the results of an 18-month study, the first of its kind in eight years, which shows that most arts organizations in the area are relatively new, small and, as a group, attract several million patrons a year.

The foundation studied 342 arts organizations out of a field of 450 for what it calls "one of the most comprehensive data bases ever assembled on an arts community." The study was directed by arts consultant Francis Harper. Groups included in the study ranged from large organizations like the Corcoran and the National Symphony Orchestra to photo clubs. The Smithsonian was excluded from the survey because its mammoth federal budget would have skewed the numbers.

Although the study draws no conclusions, "there were confirmations of things suspected by people," said Harper. "Groups would like attendance to be increased, which they think could be done by promotion and better media coverage."

According to the study, many of the smaller groups live a "catch-as-catch-can existence" with individual members often chipping in. The majority predict a need for more space in the next three years and say they already need more personnel, but can't afford it. "Well over half of these organizations have no full-time personnel," says the study. "Of those that do, many have only one employe, and that one person must function as artist, administrator, teacher, fund-raiser and publicist."

Data was collected in the fall of 1980 and spring of 1981, so the study does not reflect the effects of the Reagan cuts in government arts funding that took place in late 1981. For instance, the survey notes that in 1979 1,000 arts organization employes were "paid for under the Comprehensive Employment and Training Act," a program virtually eliminated by the Reagan administration. "How the gap created by the elimination of funding for these positions will be filled is uncertain, although it is clear that organizations will be seeking to make up the income gap not through revenues but through increased contributions from sources already hard-pressed with increased demands from their existing constituents."

The study also found:

* 76.3 percent of arts organizations surveyed were established in the last 20 years, over half in the last 10 years.

* The 10 largest arts organizations surveyed reported a total income of $30.9 million in fiscal 1980: 44.9 percent was earned income; 20.4 percent was from federal, state and local government sources; 28 percent was from private and foundation contributions and benefits; and 6.6 percent from such funds as investment income, interest, and principle transferred into operating funds.

* The majority of the groups had small budgets, with 64 percent under $25,000 in fiscal 1979. Eighty percent had budgets under $100,000, and 3 percent had budgets in excess of $1 million.

* In fiscal 1980, 7.2 million people attended exhibitions, performances and events in the metropolitan Washington area. Again, that excludes the Smithsonian. Local residents accounted for 91 percent of that figure, 8 percent were visitors from other places in the U.S. and 1 percent were international visitors.

* There were 12,389 paid staff employed by the organizations surveyed. Of these staff positions, 1,303 were full-time; 11,086 were part-time.

The 5-year-old Community Foundation of Greater Washington--a public, nonprofit foundation with funds from many sources--is the newest community foundation in the nation. Last year, it made grants of close to $300,000, according to foundation president Lawrence Stinchcomb. The foundation is not just a grant-making organization, Stinchcomb said. "The Community Foundation will play a larger role as a convener, a broker," Stinchcomb said. "We're neutral turf. That's why we can do the cultural study. If a corporation did this, people would ask, 'Why are they doing it? What's in it for them?' "