When press-through-package (PTP) sheets of similar appearance are divided into smaller sizes, their similarity increases. This in turn increases the probability of recognition errors. We created images of units of 10-, 6-, and 2-tablet PTP sheets of different colors and designs using a personal computer and then reduced their sizes in ve steps. These images of different sizes were then arranged horizontally and presented to the study participants. Differences in recognizability were determined based on the percentages of correct recognition of the size differences. A logistic regression analysis showed that there were no interactions between the packaging units and the image reduction ratio to the original sizes of the PTP sheets. However, with respect to the main effect of the packaging units themselves, significant differences were observed based on the color or design of the PTP sheet, and recognizability deteriorated as the PTP sheets were further divided. As for the percentage of correct answers, right-left differences were observed in the identi cation of the presented images; this suggests the effect of ocular dominance.