Computer-generated objects presented on a display typically have the same focal distance regardless of the monocular and binocular depth cues used to portray a 3D scene. This is because they are presented on a flat screen display that has a fixed physi-cal location. In a stereoscopic 3D display, accommodation (focus) of the eyes should always be at the distance of the screen for clear vision regardless of the depth portrayed; this fixed ac-commodation conflicts with vergence eye movements that the user must make to fuse stimuli located off the screen. This is known as accommodation-vergence conflict and is detrimental for user experience of stereoscopic virtual environments (VE), as it can cause visual discomfort and diplopia during use of a stereoscopic display. It is believed that, by artificially simulating focal blur and natural accommodation, it is possible to compen-sate for the vergence-accommodation conflict and alleviate these symptoms. We hypothesized that it is possible to compensate for conflict with a fixed accommodation cue by adding simulated focal blur according to instantaneous fixation. We examined gaze-contingent depth of field (DOF) when used in stereoscopic and non-stereoscopic 3D displays. We asked our participants to compare different conditions in terms of depth perception, image quality and viewing comfort. As expected, we found that monocular DOF gave a stronger impression of depth than no depth of field, stereoscopic cues were stronger than any kind of monocular cues, but adding depth of field to stereo dis-plays did not enhance depth impressions. The opposite was true for image comfort. People thought that DOF impaired image quality in monocular viewing. We also observed that comfort was affected by DOF and display mode in similar fashion as image quality. However, the magnitude of the effects of DOF simulation on image quality depended on whether people asso-ciated image quality with depth or not. These results suggest that studies evaluating DOF effectiveness need to consider the type of task, type of image and questions asked.