"How do you just walk out of a facility with a computer?" said Marylin Farrell.
Police say the theft happened sometime Monday at Inspira Medical Center in Vineland, New Jersey.
They say it was taken from an unsecured filing room in the radiology department.
The computer had two 250 GB hard drives and a backup hard drive with the ability to store a lot of data.
A hospital spokesman says they're investigating and don't know yet if the computer contained confidential patient records.
However patients are concerned.
Farrell had an x-ray there recently and is scheduled for back surgery.
"That type of information is confidential, there's no ifs, ands, or buts about it. I'm concerned because I'm getting surgery here on Thursday," said Farrell.
Alexis Conde's mother is a patient there. He says she heard about the stolen computer and is now concerned about identity theft.
"That's a bad rap for this hospital. They gotta get more security," said Conde.
Police say the computer was password protected but patients worry that clever thieves can get around that.
"I'm really concerned, if a computer can walk out then nothing is safe anymore," said Farrell.
The hospital says it's IT experts are working to determine exactly what information was stored on the stolen computer. So far, they haven't alerted patients to a possible security threat.