Juvenile Police Records?

It will be shown in your file that you were cautioned so that if you offend again, they can see that its a pattern of behaviour, but I think that once you are 18 the file is exponged unless the offence commited was serious, the police keep records for up to 7 years and it can be bought up in court if you repeat offend for the same thing even though you were legally cled as a minor at the time, (helps the prosecution to show a pattern of behaviour) then it goes to film and it wont show up even if you do the same thing again, but it does take 7 years, but thats in Australia and each country has different laws, its best to ask the police who cautioned you in the first place that way you'll know for sure, hope this helps you, goodluck and be good! :)