The 32-year-old hotel heiress stunned the cancer-sufferer fan, Christina, when she visited the ward at Children's Hospital in Los Angeles to wish her happy birthday, reported Contactmusic.
The star chatted and posed for pictures, which she posted on Instagram alongside the caption.
"Made me so happy to surprise the Birthday Girl Christy today at Childrens La. Such an amazing feeling to make someone smile," she posted.
"Loved being with you all today at ChildrensLa. Sending everyone love & prayers that you all get better soon. Happy to see you all smile. Stay strong. Love always Paris," she wrote.