WHIPPS Cross University Hospital has confirmed that a computer containing the details of as many as 550 patients has been stolen.
The computer was taken on February 22 and contained details including name, date of birth, treatment information and diagnosis.
It did not include details of home addresses and was protected by a password.
A spokeswoman for the hospital said: "The Trust has launched a full investigation into the theft.
"Despite there being no evidence that any data has been accessed, the Trust has contacted all patients potentially affected in writing."
CCTV footage of the area where the computer was stolen has been handed to police and an appeal has been launched for information regarding the theft.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here