Perceptual simulations are unconscious and automatic, whereas perceptual imagery is conscious and deliberate, but it is unclear how easily one can transfer perceptual information from unconscious to conscious awareness. We investigated whether it is possible to be aware of what one is mentally representing; that is, whether it is possible to consciously examine the contents of a perceptual simulation without information being lost. Studies 1 and 2 found that people cannot accurately evaluate the perceptual content of a representation unless attention is explicitly drawn to each modality individually. In particular, when asked to consider sensory experience as a whole, modality-specific auditory, gustatory, and haptic information is neglected, and olfactory and visual information distorted. Moreover, information loss is greatest for perceptually complex, multimodal simulations. Study 3 examined if such information loss leads to behavioral consequences by examining performance during lexical decision, a task whose semantic effects emerge from automatic access to the full potential of unconscious perceptual simulation. Results showed that modality-specific perceptual strength consistently outperformed modality-general sensory experience ratings in predicting latency and accuracy, which confirms that the effects of Studies 1 and 2 are indeed due to information being lost in the transfer to conscious awareness. These findings suggest that people indeed have difficulty in transferring perceptual information from unconscious simulation to conscious imagery. People cannot be aware of the full contents of a perceptual simulation because the act of bringing it to awareness leads to systematic loss of information.