We prefer some visual images or photographs but not others. Preference for these visual items is different from person to person and could be related to emotion that is generated when they see these items. In this study, we tried to understand what components affect preference for visual items and what neural mechanism participates in preference judgment of visual items. The orbitofrontal cortex has been known to participate in preference judgment of human faces or paintings and photographs. Therefore, we focused on the function of the orbitofrontal cortex. Two Japanese monkeys were used as subjects. Previous behavioral studies using 50 photographs obtained from the FMD database revealed that both monkeys exhibited clear preferences for some photographs and that preference rank order can be constructed for each monkey based on the chosen ratio of each photograph during performance of a simple choice task. In addition, both monkeys preferred sharp images compared with vague images. In the present experiment, we examined whether the orbitofrontal cortex participated in preference judgment of these 50 photographs or not. We collected visual responses of orbitofrontal neurons and examined whether or not orbitofrontal neurons exhibited positive or negative correlations between the magnitude of visual responses to 50 visual stimuli and behaviorally determined preference rank orders of these visual stimuli. We collected 188 single-neuron activities from the orbitofrontal cortex of two monkeys. Among them, 65 neurons exhibited visual responses to 50 visual stimuli and exhibited stimulus selectivity. One third of these neurons exhibited either positive or negative correlations between the magnitude of visual responses and behaviorally determined preference rank orders of visual stimuli. Among 25 neurons whose visual responses were examined under two or three conditions (using original, monochrome, or colored vague stimuli), about a half of these neurons changed the magnitude of visual responses among these conditions. These results suggest that the orbitofrontal cortex participates in preference judgment of visual items and that the difference of response magnitudes to visual items in orbitofrontal neurons represents preference for them.