Dana Hill is one teenager whose parents surely will never tell her to act her age. Though she turns 18 on May 6, the baby-faced actress, scarcely 5' tall and all of 82 pounds, has cornered the market on playing 13-year-olds. In director Alan Parker's (and screenwriter Bo Goldman's) harrowing study of divorce, Shoot the Moon, she almost steals the film from co-stars Diane Keaton and Albert Finney. The Washington Post flatly—and correctly—says that Dana, as a daughter traumatized by her parents' breakup, gives "one of the greatest adolescent performances ever filmed." It's all the more amazing that Dana achieved the sublime while working full-time on the ridiculous—she was shuttling between Moon's Marin County set and her role as the pop-off pipsqueak in the CBS sitcom The Two of Us. Last year her wrenching performance as a child porn victim helped make CBS' Fallen Angel the highest-rated TV movie of 1981. "I don't mind playing a part younger than my age," Dana says. "It's the role that counts."

If that's so, then her most moving part surely is The Dana Hill Story. The fact is, Dana's small stature stems from childhood diabetes, which has delayed her maturation. The condition was discovered at 10. At the time, Dana, always highly competitive, was the only girl on her youth-league basketball team in suburban L.A. She was into scholastic swimming and track as well. In a Southern California meet she placed third nationwide in the 880-yard run and fourth in the mile. Her father, Ted Goetz, 53, a producer of TV commercials (Chrysler, Kellogg's), recalls one meet in which Dana, at 10, raced against one of the nation's top-ranked girls. "Dana had this look on her face," her dad remembers. "Nothing could beat her, and she won."

A few weeks later, however, Dana collapsed on the track. Tests revealed her diabetes. Unchecked, it ultimately could have damaged her blood vessels, eyes, kidneys and nervous system. "I was really mad at first," Dana remembers. "I didn't want to accept the restrictions." Until she adapted to the sugar-free diet and daily insulin shots, she fell ill and was hospitalized several times. "About the same time, her growth slowed," says her father. "It seemed all her teammates were getting taller and stronger, and she wasn't. The prognosis is she won't grow anymore. It stopped her athletic career."

But not her drive. At Cal Prep High School in Encino she became as intense about acting as she had been about sports. "One day my dad mentioned that Mary Tyler Moore also suffered from diabetes," Dana recalls. "She could do everything I wanted to do—comedy, drama, dancing, singing. I've never met her, but she's been my idol ever since." Her parents tried to discourage her from acting. "They wouldn't hear of it," Dana says. "My father said it was too hard on kids."

Ironically, her dad later provided her first break. In 1973, unable to find a kid who could twirl a basketball on one finger for a YMCA TV commercial, he asked Dana whether she could. "Of course," she lied, then secretly practiced for hours and did the job perfectly next day with Boston Celtics star Dave Cowens. She later filmed six commercials and graduated in 1979 to a spot on TV's The Paul Williams Show. Dana's mother, Sandy, 48, helped her through TV commercials and guest spots but "cut the cord" for Shoot the Moon. "She brought that from within herself," Mom says.

No doubt it was in the genes. Dana was born into a Los Angeles showbiz family. Her paternal grandfather was a sea captain whose five sons all went into some aspect of films. Her great-uncle, William Goetz, married the daughter of Louis B. Mayer and became a vice-president of 20th Century-Fox and later an independent producer. "We didn't want Dana to be accused of nepotism," explains her dad, "so she uses her mother's maiden name, Hill."

With Dana's acting success, there now is less cause for sibling rivalry with brothers Matthew, 15, and Daniel, 13. "When she was into sports," explains Matthew, "she was always so good that we were looked at as 'Dana's younger brothers.' " A straight-A student at Cal Prep, Matthew is more interested in medicine than showbiz. Young Daniel, though, is about to follow Dana into TV commercials.

The family (plus five cats and an Irish wolfhound named Liza) live in a spacious San Fernando Valley home just minutes from the studio where Dana shoots The Two of Us. She drives to work in a 1979 VW convertible purchased with her earnings. Highway police stop her occasionally because she looks too young to drive. "They're embarrassed afterward," she shrugs.

Dana's fresh appearance is also a pain at R-rated movies and parties where people say, "This kid isn't old enough to be here." Men? "I haven't had that many crushes yet," Dana says, "except Tom Selleck." The boys she does date are "mostly 16 or 17," she adds shyly. "Dana is just beginning to mature," says her mother. "It's going to take a very special man to marry her. She knows exactly where she's going and she has a mind of her own." That means she has no intention of competing with teen nymphets on-or offscreen, except maybe when Oscar time rolls around next year. "I'm not in any hurry to play seductive ladies," says Dana. "I have plenty of time for that."