The study suggests that prevention efforts should target younger children, Dalton said. It was published Monday in the September issue of Archives of Pediatrics & adolescent Medicine.

The study included 120 children, ages 2 to 6. An adult researcher led a standardized play activity in which each child, acting as a Barbie or Ken doll, shopped for a visiting friend. A store stocked with 133 miniature items gave the children choices including meat, fruit, vegetables, snacks, nonalcoholic drinks, cigarettes, beer and wine.

The children could "buy" anything they wanted by filling a small grocery cart and taking it to a small checkout counter.

Twenty-eight percent of the children bought cigarettes, and 61 percent bought alcohol. The children whose parents smoked were almost four times more likely to buy cigarettes. The children whose parents drank at least monthly were three times more likely to buy alcohol.