Staffordshire Police has warned festival goers about buying tickets from unofficial websites after customers reported ticket scams.
Hayley Parsons, of Ludlow, Shropshire, spent £1,500 on seven tickets for V Festival, which is being held at Weston Park, Staffordshire, this weekend.
The 23-year-old said the tickets had not arrived and the website she booked through no longer existed.
Police said they were investigating many fraudulent websites.
Miss Parsons was diagnosed with a brain tumour in 2008 and had planned to go to the festival with her friends to celebrate her recovery.
It would have been her first concert experience.
She said: "I wanted to go to V to relax and celebrate that I had made it through, because things could have gone the wrong way, but of course it's all been taken away from me."
Jackie Butcher, from Tamworth, Staffordshire, bought a ticket online in March for her son's 16th birthday but it has also not arrived.
A spokesman for the force said: "Staffordshire Police is aware of a number of fraudulent websites connected to fake tickets.
"The investigation of fraudulent websites is being progressed at a national level by the Metropolitan Police force.
"Fraudulent websites are being developed all the time and this information is being passed on to be investigated."