Fast food outlet KFC has lodged an appeal against a payout for a child who was left severely brain damaged after eating a chicken wrap.

In April, Justice Stephen Rothman ordered KFC Australia to pay Monika Samaan's family $8 million.

During a month-long court case in Sydney, the restaurant chain denied it was responsible for her injuries.

The 14-year-old was left with severe brain damage after contracting salmonella poisoning when she ate a chicken Twister at the Villawood KFC in Sydney's west in 2005.

She was in hospital in a coma for six months and now cannot speak and is mostly confined to a wheelchair.

Miss Samaan was seven when she went to KFC with her family to get the food.

Her family says the payout will be used for medical care she will need for the rest of her life.

But lawyers for KFC have lodged an appeal in the New South Wales Supreme Court questioning aspects of Justice Rothman's findings.