In the Ebbinghaus Illusion, the size of surrounding inducers influences the perceived size of the target. The illusion is strongest when targets and inducers belong to the same category. This conceptual similarity effect might stem from increased attention toward similar inducers. To explore this hypothesis in Experiment 1 target faces were surrounded by inducers that matched targets in one or two dimensions (sex, emotion). Instructions emphasized one dimension (e.g., emotion). I predicted participants would attend more to inducers that matched targets in the instruction-relevant dimension, and this would modulate the targets' perceived size. However, eye-tracking revealed no differences in attention, and behavioral reports showed no modulation of perceived size. In Experiment 2, more direct instructions effectively biased eye fixations toward certain inducers, but such attentional increases failed to bias the target's perceived size. These studies showed no evidence that the conceptual similarity effect is mediated by visual attention.