Scott Routley, who was believed to have been in a vegetative state for 12 years, was able to tell scientists that he is not in any pain at the University Hospital in London.
It's the first time an uncommunicative, severely brain-injured patient has been able to give answers, reports the BBC.
Routley, who suffered a severe brain injury in a car accident 12 years ago, was asked questions while having his brain activity scanned in an fMRI machine.
British Neuroscientist Professor Adrian Owen, who led the team at the Brain and Mind Institute, University of Western Ontario, told the BBC: "Scott has been able to show he has a conscious, thinking mind. We have scanned him several times and his pattern of brain activity shows he is clearly choosing to answer our questions. We believe he knows who and where he is."
"Asking a patient something important to them has been our aim for many years. In future we could ask what we could do to improve their quality of life. It could be simple things like the entertainment we provide or the times of day they are washed and fed."
Routley's parents always thought he could communicate by lifting a thumb or moving his eyes, but that was never been accepted by his doctors.
Routley's doctor, Professor Bryan Young, told the BBC: "I was impressed and amazed that he was able to show these cognitive responses. He had the clinical picture of a typical vegetative patient and showed no spontaneous movements that looked meaningful."