Children everywhere are fascinated by scary things, and child-development experts assure us that fantasies are good for them.

Enacting roles, particularly for preschoolers, helps children come to grips with their own aggression, control, helplessness and fears.

Parents, teachers and specialists have all observed that monsters frequently, and not coincidentally, behave in ways that children would like to act. A 3-year-old -- disguised as a dinosaur -- for instance, might find himself nibbling a new sister's arm or leg.

When a youngster becomes a super being, be it monster or hero, he is instantly powerful and competent, able to overcome all odds. Scary animals, siblings, dominant adults, thunderstorms, etc. -- all of which occasionally leave a preschooler feeling tiny and helpless -- are conquered by a conquering beast. Through such dramatic play, often repetitive in theme and content, the child begins to manage his fears.

"Halloween," says psychotherapist Robert Royeton, "provides him with a publicly endorsed opportunity to deal with these feelings, following the same psychological process he uses in everyday imaginary play.

"By becoming an imaginary character, he tames those forces that threaten to overwhelm him," says Royeton, of Walnut Creek, Calif., in an October Parents magazine article on the value of make-believe.

But what if a creep becomes too creepy? Some suggestions from parents and other experts:

* Help your preschooler distinguish real from pretend. Preschoolers, particularly in the 2- to 3-year-old range, may suspect that a Halloween monster will turn on them. Assure your child that creatures born of her imagination -- and that of others -- however wild and wicked, are not real. At trick-or-treat time, ask costumed friends to remove their masks, if only for a minute, so that a little one can see that the ferocious tiger is really nice Jenny from next door.

* Listen to what is frightening. Encourage your children to express their fears and acknowledge them: "I know it's a pretend monster, but it really scared you, didn't it?"

* Enter the fantasy, if you're invited. With your child as the guide, learn about the monsters and heroes that inhabit his special world. Your child will feel he has a wonderful companion, and you will have a terrific time meeting the beasties.

* Help banish the monster, when it's time. When (and if) your child indicates that she is ready to say good-bye to an imaginary character that has been lurking around for a while, you might be invited to participate in its demise. Wonder aloud how you might do away with a troublesome dragon, for instance, or help your child bake a good-bye cake -- or trounce -- the critter that has been plaguing her. Don't, however, eliminate any creatures your child still seems to need. Hastily banished beasts will reappear again.

* Read about how other children have handled their monsters. Two good books with which preschoolers will empathize: Maurice Sendak's Where the Wild Things Are and Mercer Mayer's There's a Nightmare in My Closet.

And remember that sometimes the most terrifying vampire can be vanquished with a hug.