The Montgomery County Zoning Appeals Board has denied a bid by Suburban Hospital to build a six-story, 84,000-square-foot ambulatory care facility and helicopter pad on land adjacent to the hospital on Old Georgetown Road in Bethesda.

The decision last week, which was almost a year in coming, disappointed hospital officials because three of the four voting members on the appeals board agreed to approve the structure. A fourth, board Chairman Thomas S. Israel, dissented, saying the structure was not a hospital addition and therefore not covered under the county's special exception ordinance.

Because county zoning law requires four affirmative votes in a special exception case, Suburban's request was rejected. The fifth member of the zoning board abstained because she had not heard the case as it was presented.

The hospital is now considering "whether to live with the decision or appeal it to the Montgomery County Circuit Court," said Bob Dalrymple, one of the lawyers representing Suburban.

The zoning appeals decision came three years and numerous revisions after Suburban first declared such a facility was necessary if the hospital was to respond to a growing demand for outpatient treatment.

Neighbors in the Huntington Terrace Citizens Association mounted vigorous opposition, claiming the size and bulk of the proposed 45-suite building was incompatible with single-family homes.

They said the additional traffic from an outpatient clinic would ruin their neighborhood.

The residents said the community, which is near the massive National Institutes of Health complex, has been inundated for years with medical and professional office buildings, all seeking the prestige of a Bethesda address and proximity to NIH.

In his dissent, Israel argued that ambulatory care centers are not hospitals but rather medical clinics and, as such, are not allowed under the county's special exception ordinance.

He said hospital developers seeking these buildings on their premises may have to seek a special zoning amendment to cover them. Holy Cross Hospital in Silver Spring, another applicant for the same kind of medical building, postponed its hearing before the Montgomery Planning Board this week following the Suburban decision and in the face of mounting neighborhood opposition.

Montgomery County planner Dennis Canavan said, "Presumably, they asked for the March 24, 1988, hearing date when they found out we were recommending denial of the Holy Cross proposal. This gives them enough time to try and change the zoning ordinance."

A hospital spokesman said Holy Cross asked that the hearing be delayed at the last moment because "we understand the planning board is going to draft a text amendment that will recognize ambulatory care centers."

Canavan and other planners said they have no such plans.

Meanwhile, residents near both hospitals remain adamant in their opposition. Neighbors near Suburban celebrated their victory last week, but opponent Spring Swinehart said she assumes "that Suburban will appeal and the fight will be on again."

Neighbors near Holy Cross are also united against what they call "development by special exception," according to resident Dwight Fortna.

Said Norman Knopf, the lawyer for residents fighting the Holy Cross expansion, "If the hospital wants to nurse the sick, that's fine. But let them do it on Georgia Avenue where it's zoned commercial."