Her voice choked with emotion, Nancy Reagan wiped back tears, thanking 2,000 cheering teen-agers for their enthusiastic reception of 15 first ladies from around the world who she brought here today for an international conference on drug abuse.

"You are our future," she declared, clutching a red rose, tears streaming. "We depend on you. We need people who are clear-eyed, clear-minded . . . I'm so proud of you. And I love you."

"WE LOVE YOU," they shouted back.

She flew here from Washington as part of a two-day summit on drug abuse to let parents "around the world know they are not alone" in the fight against illegal drugs. "Mothers and fathers are the same the world over," she said. "They love their children."

It was a trip designed to give 15 first ladies a chance to hear teen-agers, medical experts and educators from 40 countries parade forth solutions to the world-wide drug epidemic. They sat in the front row in a cavernous ballroom at the Georgia World Congress Center, with non-English-speaking first ladies getting translations through headsets.

Two of the 17 first ladies who had gathered in Washington were unable to make the trip to Atlanta, said Jennefer Hirshberg, press secretary for Mrs. Reagan. Maria Lorenza Barreneche de Alfonsin of Argentina did not feel well enough to leave Washington this morning. And Joan FitzGerald of Ireland, confined to a wheelchair, never planned to come.

Only first ladies whose countries had sent representatives to earlier conferences sponsored by PRIDE, an Atlanta-based anti-drug education group that deputizes parents and teens as combatants in the war on drugs, were invited.

It was at a similar gathering three years back that Mrs. Reagan said she suddenly saw "how we could save our children from drugs." Until then, she'd seen "the pain our children were suffering, but I hadn't seen the answer . . . "

Soon, she was in hot pursuit of the anti-drug issue, and her crusade shifted into high gear while political cynics suggested that it was a way to alter the image of a first lady who appeared hooked on high fashion.

There was plenty of evidence here today that her message was not only trickling down to teen-agers, but appreciated. They greeted her like a favorite rock star.

"It's better hearing it from her than any other adult," said Stephanie Hudson, 15, a 10th-grader from Columbus, Ga. "She was inspiring."

"She was so cute," cooed Kim Preston, 17, also from Columbus. "Drug attitudes have changed. We have more friends who don't do them than do. But if they do, they do it in private. It's not something people are proud of."

Alcohol appears to be the new drug of choice, said teen-agers at the conference. But, said Hudson, "A lot of kids I know ask their friends to drive them home if they've been drinking at a party."

There was dancing in the aisles as a group of smiling, well-scrubbed teens in red and blue sweatshirts and white slacks entertained the first ladies with rock songs, gymnastics and testimonials. But it was Steve Courtney, 17, of Overland Park, Kan., whose crooning brought tears to Nancy Reagan's eyes. She gave him a big hug, as the crowd cheered.

"When she cried, I was really touched," said Cynthia Sheevin, 15, of San Antonio. "It showed she really cared."

Earlier, Carlton Turner, a special assistant to President Reagan for drug-abuse policy, told the conference he favored the death penalty for drug dealers in some cases. "Drug dealers have no mercy for their victims and we should have none for them," he said. " . . . In some instances I believe the death penalty is warranted."

The conference offered workshops for teen-agers on how to organize peer groups to fight drug abuse, and a host of speakers detailed new evidence of health damage from marijuana, cocaine and other illicit drugs. Jean-Michel Cousteau narrated a documentary he made in South America, "Snowstorm in the Jungle," about the effect drug smuggling has on peasants of exporting nations.

"Hopefully, these first ladies won't make all the mistakes we made" tackling the drug problem, said Thomas Gleaton, a PRIDE cofounder, in an interview. "Like (debating) whether marijuana is addictive." He said experts now believe it to be a "gateway drug," the first step to even more serious drugs like cocaine.

The first ladies lunched on fresh asparagus, sliced duck, beef tenderloin and the new Coca-Cola, served over ice by waiters. The host was Atlanta-based Coca-Cola, which long ago purged the Real Thing of alkaloids from the coca leaf. One company official said Mrs. Reagan sipped the new Real Thing and wondered how it differed from the old.

Upstairs, the old days were definitely out as Secret Service men frisked Christian Edwards, 18, an Atlanta high school senior who showed up in ripped jeans, T-shirt and an earring, a flashback to the '60s. He blamed a permissive home life for his early drug use -- he first smoked marijuana at eight -- but said he'd cut way back.

"My mother was a hippie," he said.