While most children like sweets, those with an extra-sweet tooth may be depressed or at higher risk of future alcohol problems, researchers say.
The US team report in the journal Addiction that certain children are especially drawn to very sweet tastes.
These were children who had a close relative with an alcohol problem or who themselves had symptoms of depression.
But it is unclear if the preference for the very sweet is down to genuine chemical differences or upbringing.
The researchers say sweet taste and alcohol trigger many of the same reward circuits in the brain.
Lead author Julie Mennella said: "We know that sweet taste is rewarding to all kids and makes them feel good.
"In addition, certain groups of children may be especially attracted to the intense sweetness due to their underlying biology."
Experts say alcoholics tend to have a sweet tooth.
But the link is less clear in children. Other US researchers have shown that a preference for the sweetest drinks was found in the ones undergoing growth spurts.
In the latest study, the scientists at the Monell Chemical Senses Center asked 300 children aged five to 12, of whom half had a family member with alcohol dependency, to taste five sweet water drinks containing different amounts of sugar.
The children were asked to say which tasted the best and were also asked questions to check for depressive symptoms.
A quarter had symptoms that the researchers believed suggested they might be depressed.
Liking for intense sweetness was greatest in the 37 children who had both a family history of alcoholism and reported depressive symptoms.
These children preferred the drink containing the most sugar - 24% sucrose, which is equivalent to about 14 teaspoons of sugar in a cup of water and more than twice the level of sweetness in a typical cola.
This was a third more intense than the sweetness level preferred by the other children.
The researchers then decided to test whether the children's taste difference had any impact on their reaction to pain or discomfort - past studies have suggested sweets may help act as analgesics as well as mood lifters.
They found non-depressed children were able to tolerate keeping their hands in very cold water for longer if they had a sugar hit.
However, the extra sugar did nothing to the depressed children's pain threshold.
Cardiff University's Professor Tim Jacob, an expert in smell and taste, said the findings were interesting, but that it was hard to make firm conclusions or generalisations from one study alone.
He said the findings could be down to brain chemistry, but might also be explained by behaviour and upbringing.
"While it is true that sweet things activate reward circuits in the brain, the problem is that sweets and sugar are addictive, because the activation of these reward circuits causes opioid release, and with time more is needed to achieve the same effect.
"But the taste difference may be explained by differences like parental control over sweet consumption."