Q. My husband and I are deeply puzzled by something that also bothers many of our friends: the movies our children watch on TV.

We don't allow our children, ages 8, 10 and 12, to watch a great deal of television, but we do have cable and, of course, they watch movies on that. In addition, they see rented video cassettes of movies at the houses of friends.

Is there any guide that will tell us what we need to know about the movies on cable or on video cassettes? So many of them are highly unsuitable for young people.

Also, our kids push to see a lot of these movies anyway, and they say, "Mom, it's only a movie!" Do you think movies have an impact on kids' feelings and values? And if so, what can we do to counteract their adverse effects?

A. Parents aren't helpless at all, not about television or anything else.

You're not only older and taller and pay the mortgage, but as parents, you have the right -- and the responsibility -- to decide what movies your children see, anywhere.

This doesn't, of course, mean that they'll always follow your wishes or that you can resolve the problem just by taking a firm stand.

Children try so hard to conform to their friends -- and liberate themselves from their parents -- that it's hard for them to say no to an "R" movie at a friend's house, especially when the parents give tacit approval by having it in the house. And as for a PG movie: Forget it. Parental guidance has somehow been translated to parental give-in.

Since movies can affect your children's values and feelings, the movies must be monitored, wherever they're shown.

To choose the right movies for your children, you want to consider them from many viewpoints, including prejudice, for some movies subtly put down women (or men or children), or races or religions.

Sex scenes may bother you more than your children -- who will be teen-agers before they make complete sense out of them -- but you still don't want them to see explicit shots. To most parents, violence is the big offender in movies.

Very young children, who often think of animals as if they were people in disguise, may be frightened by the old Tom and Jerry style cartoons and "Snow White" can give them the weeps. But it's in the middle years, between 6 and 12, that mindless, gratuitous violence should be banned, especially when it's combined with sex.

Other violence may only be implied, but it still must be monitored.

All children are frightened by the supernatural, but when it passes that delicious point of tension, or when it hits a child's special vulnerability, the movie can haunt that child for years. Consider the effect of a movie about kidnaping on the child who is secretly afraid her missing father will steal her away. And that's why parents need to be extra careful.

Since children keep their fears to themselves at this age, you may not know what they are. It's only sensible to ban movies that you think could upset them, regardless of whether the children say they do not.

To find out which ones they are, add Lynn Minton's excellent Movie Guide for Puzzled Parents (Delta, $12.95) to your family library. It seems to be the only book that assesses movies made for the theater, cable and TV and does it from a parent's point of view. Her reviews of the latest movies are carried in McCall's magazine.

And when your children occasionally see the wrong movie anyway -- and they will -- it won't be the end of the world.

For all the power that movies can wield, you have much more. No one matters more to a child than his or her parents -- and no people matter more to parents than their own children. And yet it is rare that either side has any idea how much the other really cares. This lack of communication is one of the most astonishing aspects of our media-happy families: We talk, but we don't say much.

By discussing movies (and television and magazines), you have a great chance to open doors that might have stayed shut. You handle a questionable movie the way you handle a shocking story on the evening news or a dumb ad that promises nutrition in a junky cereal.

You talk about it. You ask what they think and why. You say what you think. You make jokes. You discuss the subject with them the way you would with an equal, for in an intellectual discussion, children are equals. They have smaller frames of references, but they still can think and they still have the right to their opinions. And you have the right to prevail.