As the charity's Royal patron, she saw the unit in action in Cwmbran, during one of its regular visits to deliver support, advice and treatment to cancer patients across South Wales.
During her visit, the Princess viewed the unit's latest facility - a touch screen visitor questionnaire, developed by EMS to capture key lifestyle information for the Great Welsh Health Check initiative.
"It was a great opportunity to show our Patron the work of the mobile unit and she was extremely impressed with the facilities we are able to offer local people," said Mobile Unit Manager Duncan Innes.
"The last thing people want when they undergo often gruelling cancer treatment is a long trip to hospital, and the unit helps a great deal in reducing stress for our patients."
To comment register and let us know your thoughts.