Reported cases of anti-Semitic vandalism and violence increased in 1984, and the number in Maryland was exceeded only in New York and California, the nation's most populous states, the Anti-Defamation League of B'nai B'rith reported yesterday.

Sally Greenberg, assistant director of the league's Washington area office, said the number of incidents reported in Maryland was probably greatest in Montgomery County, based on figures from the county's Human Relations Commission. A county-by-county breakdown of her own organization's statistics was not available.

Of the 715 incidents reported nationally -- a 6.7 percent increase over 1983 -- the league said 69 occurred in Maryland, a 49 percent increase over the 47 incidents reported there the year before.

In New York, 237 incidents were reported, while 99 were reported in California, according to the ADL. Greenberg said 10 anti-Semitic incidents were reported in the District of Columbia and nine in Virginia.

Joan C. Weiss of the Montgomery Human Relations Commission, which calculates its statistics differently than the ADL, said 69 anti-Semitic incidents were reported in the county last year. include 38 reports of harassment that ADL figures omit.

Weiss said 48 incidents were reported in the county in 1983, and 95 in 1982. "We'd always like to see a decline, rather than an increase," she said, but called it "heartening and encouraging" that the 1984 figures remained well below the 1982 level.

Greenberg said concerted efforts in Maryland, and especially Montgomery County, to make people aware of the problem of anti-Semitic incidents may have encouraged more people to report them.

In addition, she said, a large Jewish population and the large number of prominent Jews may cause a larger number of anti-Semitic incidents, she said. Montgomery County has almost 87,000 Jewish residents, according to a recent study, about 14.5 percent of its total population.

"When Jews are fairly visible, and in an official capacity, it makes them easy targets," she said. "It's not necessarily the people who are so visible who become targets. But when people have anger, they may take it out on people living nearby."

Greenberg said the most common incidents of anti-Semitism were spray-painted graffiti on walls and bridges. Last July, for instance, swastikas were spray-painted on the Gaithersburg Hebrew Congregation in Montgomery Village. In September, anti-Semitic slogans and swastikas were spray-painted on four homes in Potomac.

Greenberg said there were no obvious answers to the problem of anti-Semitic incidents. "We feel we are doing everything we can to educate people," she said, adding that the ADL and other Jewish organizations will continue to do so. "That to me is the most important thing."