Medical, ethical, legal, and economic reasons justify the assessment of possible conscious remnants in comatose and vegetative patients. One of the issue as to whether it is possible to bypass communication and examine consciousness thanks to the recording of scalp electrical brain activities (electroencephalogram, evoked potentials) both with fMRI study, can only be achieved on the basis of an operational model of consciousness. The Oddball paradigm are often used in clinical domain to get information on (1) the integrity of stimulus analysis in sensory-specific cortex (N1-P2); (2) the patient's ability to orient his/her attention to a target stimulation (N2-P3a); and (3) cognitive processing related to memory and/or response (P3a-P3b). In this study, 3 patients in a vegetative comatose state were confronted with a classical auditory oddball P300 design during the recording of event-related potentials (ERPs) and during fMRI with the same stimuli. CEPs and fMRI data were compared in order to assess whether a brain response was generated by deviant rare stimuli, thereby providing some information on the level of the patient's consciousness. According to two recent models (the consciousness model developped by Damasio.A and the one of Guerit.J.M for the CEPs in comatose), we suggest that clinical neurophysiology in association with fMRI may be of the great help to discriminate and monitories comatose patients and more specifically in vegetative comatose patients.