Objective: Examine the influence of altering the size of snack food (ie, small vs large cookies) on short-term energy intake. Methods: First- and sixth-graders (n = 77) participated in a between-subjects experimental design. All participants were offered the same gram weight of cookies during an afternoon tea at their school. For half of the participants, food was cut in 2 to make the small item size. Food intake (number of cookies, gram weight, and energy intake) was examined using ANOVA. Results: Decreasing the item size of food led to a decrease of 25% in gram weight intake, corresponding to 68 kcal. Appetitive ratings and subject and food characteristics had no moderating effect. Conclusions and Implications: Reducing the item size of food could prove a useful dietary prevention strategy based on decreased consumption, aimed at countering obesity-promoting eating behaviors favored by the easy availability of large food portions. (Contains 1 table and 1 figure.)