WASHINGTON (AP) _ Nancy Reagan passed out kisses, hugs and 300 plush dolls Tuesday to youngsters at Children's Hospital after delivering a $25,000 check to the medical center.

Mrs. Reagan, dressed in a bright, Christmas red and green Adolfo suit, spent more than two hours touring some of the wards, playrooms and recovery rooms of the 263-bed hospital, to offer the children a bit of holiday cheer.

During her rounds of the hospital, the first lady met with children who suffered from a variety of ailments, were recovering from surgery or broken bones, and even a few who had spent the majority of their short lives in the hospital.

Handing 13-month-old Tony Steptoe a purple-haired doll, Mrs. Reagan exclaimed, ''It's almost as big as he is 3/8'' The gurgling little boy wore a long blue tie, given him by the nurses for the occasion.

Despite the intravenous tube attached to his nose, the tiny youngster jumped and waved, grabbing at Mrs. Reagan's golden necklace. One of the nurses joked that the exuberant tot appeared to want an invitation to the White House. Mrs. Reagan laughed and asked, ''To a state dinner?''

''I'll see you at the White House,'' she added, patting the little boy on the head as she left the playroom.

The first lady knelt down to speak with many of the children, speaking with each one - or its parent if the child were an infant - as she delivered the fuzzy dolls.

Even as Mrs. Reagan was engulfed in giving and receiving hugs and good wishes from the children, a controversial subject popped up.

''I love your 'Star Wars' missiles,'' 9-year-old Rashid Graham blurted out to Mrs. Reagan as she bent over the youngster, swaddled in a hospital gown and sitting in a wheel chair.

Rashid said later the first lady told him she would give his message to President Reagan about his proposed missile defense system. ''If there is a war, he'll put us in a safe place and then he can shoot all the missiles,'' the youngster gave as his rationale for supporting the president's plan.

At one point, Dr. Barnaby Starr, the chief resident for one of the children's oncology and hematology unit, stopped Mrs. Reagan to say he was grateful she had visited one 6-year-old patient who had a severe immune problem and suffered from bouts of depression.

''It really perked the child up,'' said Starr, who also evoked a laugh from the first lady when he offered to come to Pennsylvania Avenue ''in case you're looking for a young doctor to come to a White House party.''

It was the fourth time that the first lady has made the Christmastime visit to the medical center, founded in 1870.

The check delivered by Mrs. Reagan was donated by the sponsors of the ''Chistmas in Washington'' television show broadcast by NBC on Sunday - AT& T, General Motors and USF&G Insurance.