Do you mean rather than ordinary (ie adult) ones, or whether children need them at all?
If the first, then yes! You must not give children adult vitamins as the dosages are very different, especially for mineral content, and children can get very ill if they overdose on vitamin pills.
If the second, then it probably depends on the individual child's diet. My two eat a decent diet, but ds rarely eats what I consider to be enough. He's generally fine, so I suppose eats as many calories as he needs, but occasionally gets run-down, which is when I do give him mulit-vitamins with minerals. The result is usually quite spectacular, with him returning to his normal self within 2-3 weeks.