Prince William sat down with Radio Marsden’s Barry Alston for a "truly delightful and heartwarming conversation".
The Duke of Cambridge answered some questions from young patients of The Royal Marsden NHS Foundation Trust, said a statement.
It said William also celebrated the passion of hospital staff and shared a favourite Christmas song.
Radio Marsden is a self-funded and run entirely by volunteers. It relies on donations to pay for the various licenses and equipment required to provide a top quality service to patients of both The Royal Marsden Hospitals.