Yes.  Even if the law states that you are not old enough to enter into such a contract, the credit card company can come after you once you turn 18.  Also, the credit card company may be able to sue you for fraud because you lied about your age with full knowledge that you probably wouldn't get a credit card at your age.  Your parents might also be liable for any debt that you have with the credit card company.  Finally, even if the contract is not enforceable now, the credit card company could probably get back when you got from them.  For example, if you purchased a car when you were under 18 and the contract is not enforceable, you can't be made to pay for the car, but the dealership can get the car back and possibly get you to pay for any value lost because the car is now used.