Hull University researchers claim that hypnosis' effect on the brain is so "very real" that it can be easily picked up via scans.
In an imaging study of hypnotized participants, researchers showed decreased activity in the parts of the brain linked to daydreaming or letting the mind wander.
The same brain patterns were absent in people who had the tests but who were not susceptible to being hypnotized.
One psychologist said the study backed the theory that hypnosis "primes" the brain to be open to suggestion.
Hypnosis is increasingly being used to help people stop smoking or lose weight and advisers recently recommended its use on the NHS to treat irritable bowel syndrome, reports The BBC.
The researchers said that in earlier studies it was not clear whether the changes in the brain were due to the act of doing the task or an effect of hypnosis.
In the current study, the team first tested how people responded to hypnosis and selected 10 individuals who were "highly suggestible" and seven people who did not really respond to the technique other than becoming more relaxed.
The participants were asked to do a task under hypnosis, such as listening to non-existent music, but unknown to them the brain activity was being monitored in the rest periods in between tasks.
In the "highly suggestible" group there was decreased activity in the part of the brain involved in daydreaming or letting the mind wander - also known as the "default mode" network.
One suggestion of how hypnosis works, supported by the results, is that shutting off this activity leaves the brain free to concentrate on other tasks.
Study leader Dr William McGeown said the results were unequivocal because they only occurred in the highly suggestible subjects.
He said: "This shows that the changes were due to hypnosis and not just simple relaxation. Our study shows hypnosis is real."
The study is published in the journal Consciousness and Cognition.