The purpose of this study was to examine children's age-related changes in performance and strategies in an area and volume comparison. Kindergarteners and pupils in the lower grades of an elementary school participated in this study. Pairs of rectangles or rectangular solids were presented to the participants, and they were asked to indicate which one was larger. Results showed that the percentage of correct answers in the area comparison tasks varied across age groups in a u-shaped manner, whereas the percentage of correct answers in volume comparison tasks increased in a linear manner. The results from the analyses of the comparison cues that children used revealed that the kindergarteners and first graders were unable to integrate differences in multiple dimensions, and that they utilized the differences as separated cues in the area and volume comparisons. However, second and third graders could integrate and utilize differences in multiple dimensions as comparison cues. These results support the view suggested by Bausano and Jeffrey (1975), that three-year-olds should outperform four- or five-year-olds in area comparisons because three-year-olds tend to compare areas and utilize the differences in the longest dimension as comparison cues.