About 300,000 mobile phones are stolen every year in the UK - and the police say that number is rising.
Criminals as young as 13 have been spotted on bicycles and mopeds grabbing gadgets out of people's hands.
In one area of London, Islington, mobile snatching has increased by 400% in the past 12 months.
Ricky's been finding out more about the issue and how to protect your phone from thieves.
What happens to your phone once it's stolen?
Smartphones are worth a lot of money. They're sometimes sold on to mobile phone recycling companies or sent abroad where they are worth a lot in countries like Nigeria in Africa.
If your phone has been snatched or stolen, contact the police straight away. Make sure you react quickly as the police can check local CCTV footage to try and find the criminals.
After you've contacted the police, call up your mobile phone provider and tell them to block your handset so it can't be used to make calls.
But experts say blocking your phone only stops it from working in the UK. It can still be used abroad.
Detective Superintendent Steven Wallace works in central London and is cracking down on mobile theft.
He said: "Most stolen phones are switched off straight away, the Sim card is removed and the gadget ends up in the wrong hands."
How do you stop your phone from being stolen?
Detective Superintendent Steven Wallace says it's important to be aware of your surroundings.
He says phones are usually stolen when people walk along a busy street or leave them behind in restaurants.
"You should always try to be aware of who is around you."
He adds: "The best advice is to go inside a shop to use your mobile as you'll be a lot safer. Try not to get your phone out the minute you stop off a bus or train."
The best advice is to make sure you don't wave your phone about in public.
Keep it tucked away in your bag or pocket.