Carla Weidman still remembers when her pre-school son had his first bout with night terrors.

"It was very frightening," said the Children's Hospital psychologist. "It happened in the early part of the night, before we went to bed. He was screaming and crying and yelling at all sorts of creatures in his room, pushing them away, pushing us away."

Then, as now, there was very little Weidman could do. "You can't wake them up. They're in a very deep sleep. All we could do was stay with him."

Night terrors are, in fact, more terrifying to parents than children, say experts. While relatively uncommon -- an estimated 4 percent of all children are said to suffer from them -- they are also considered developmentally normal. Children eventually will grow out of the condition, experts say.

Unlike nightmares, which occur later in the night, night terrors surface during the first two hours or so of the night, during deep sleep. Your child may have her eyes open, and her pupils may look larger than normal -- but she's not awake. If you do manage to wake your child, she probably won't remember the dream, but it's important to have the lights on so she can adjust quickly to the real world around her.

Night terrors have no story line, but usually involve fairly primitive images, such as being chased by monsters or spiders. Sometimes the child may try to get out of bed and escape, so it's important to take steps to protect the child by installing safety gates if she is prone to night terrors.

Nightmares, on the other hand, occur much later, closer to morning, during Rapid Eye Movement sleep, and involve convoluted, movie-like plots. There may be some thrashing, but no screaming or attempts to get out of bed. The child will often wake up, though, and have difficulty falling asleep again.