You may be able to. It depends on a number of factors.
However, if you can claim your son as a dependent on your federal return, you can also claim him as a dependent on your Illinois return.
According to Students: Answers to Commonly Asked Questions - Individuals, Illinois uses the same definition of a dependent that the IRS does.
Please see the TurboTax Help article Who can I claim as my dependent? for qualifying information.
**Say "Thanks" by clicking the thumb icon at the lower left
**Mark the post that best answers your question by clicking on “Mark as Best Answer”