The hospital said they hope the annual contest can offer some normalcy to the parents of premature babies.
The babies range in age from one day to 6-months-old. They're celebrating their first Halloween as lions and princesses and bears, oh my!
You can vote for your favorite pint-sized patient on Advocate Children's Hospital's Facebook page.
The winner and two runner-ups will take home prizes, but the hospital said they are all winners.