And their results may eventually lead to a test which could determine who is faking it, and who isn't.
The researchers at University College London took two brain scans of 17 male and female volunteers.
The first was taken while the subject was looking at a picture of their partner with whom they claimed to be "head over heels in love".
The second scan was taken as the volunteer looked at a picture of a friend who was the same sex as their loved one.
Dr Andreas Bartels said that looking at pictures of the partner produced activity in two distinct areas of the brain that looking at the friend did not.
Gut feelings
These were in the medial insula, a part of the brain associated with "gut feelings", and part of the anterior cingulate, associated with feelings of euphoria.
Dr Bartels said: "It's not surprising that we got a response in this particular part of the brain."
The team used a lie detector test as a way of checking the emotions of the participants - lie detectors are triggered by skin changes caused by strong emotions.
He added: "I'm convinced that we can use it as a test for love - however, it's rather an expensive one!"
This is one of the first studies to look at the brain activity associated with feelings of love - other research projects have tried to identify the parts of the brain that react to pain, fear or happiness.
The team gathered love-struck volunteers by placing posters and adverts around the university in which they work.
They were inundated with potential subjects, mostly women, and chose 11 women and six men.
Interestingly, the experiments noticed no significant differences between the reactions of men and women, although more testing may be required to verify this.
The study was presented at the Federation of European Neuroscience Societies meeting in Brighton, and reported in New Scientist magazine.