About 75 people, many of them Polish Americans, participated in a demonstration near the Polish Embassy yesterday to protest the weekend detentions in Poland of Solidarity union leaders.

"We will be back again and we will have greater numbers," said Jurek Samotyj, an organizer of a newly formed local group calling itself Friends of Solidarity.

Yesterday's demonstration was organized at Our Lady Queen of Poland Catholic Church, of Silver Spring, during the morning mass. The church is the only Polish parish for the region's several thousand Polish families.

"People were very upset and very, very sorry for all our relatives," said Father Edward Mroczynski, the pastor, who said he saw "many with tears in their eyes." Several hundred turned out for yesterday's mass, he said, a number higher than normal in a congregation of 300 families. "I asked them to pray for the country."

Demonstrators with placards saying "Communist Puppets out of Poland" or simply "Solidarity" marched at the intersection of 16th Street and Columbia Road NW, after they were told by Secret Service and D.C. police that they were barred from demonstrating closer than 500 feet from the embassy, which is at 2640 16th St. NW.

Marek and Ella Kaszubski, a couple in their 30s from Silver Spring who emigrated from Poland in 1976 in search of better jobs, said yesterday's was the first demonstration they ever attended. "There comes a time when you have to take a stand," she said. "We think what is going on is terrible and we want to show our solidarity with Solidarity."

Marek, who is a lawyer, and Ella, who works for a printing firm, said they have been expecting a crackdown on dissent in Poland, but thought it would come from the Soviets rather than the Poles themselves. "It is so very sad," he said.

Nils Brubaker, a 29-year-old computer programmer from Rockville, marched with his Polish-born daughter Natalia, 5. Brubaker met his wife while he taught English in Poland five years ago. He said he came to the demonstration "because I feel close to the Polish people . . . and I was thinking about my Polish friends." He recalled Poland's "undercurrent of dissatisfaction" among workers who complained about the cost of living and the lack of control over their work places.

Lillian Morrison, 74, of Washington, saw the demonstration as she left nearby All Souls' Unitarian Church. She decided to join the marchers in the chilly wind.

"If we support these people, maybe there'll be a loosening up in general in the Soviet bloc," she said.