Can i claim my son for half the year if he turned 18 in june?

[jerry2000]

You can not claim a dependent for half of a year, its either all year or none. Turning 18 does not prevent you from claiming him if he otherwise qualifies.

[Hal_Al]

A child of a taxpayer can still be a “Qualifying Child” (QC) dependent, regardless of his/her income, if:
1. He is under age 19, or under 24 if a full time student for at least 5 months of the year, or is totally & permanently disabled
2. He did not provide more than 1/2 his own support. Scholarships are considered third party support and not as support provided by the student.
3. He lived with the parent (including temporary absences such as away at school) for more than half the year