St. James' and St. Vincent's Hospitals raked in over 5 million euro in car parking charges last year.
In total eight Dublin facilities have failed to lower the cost of parking for cancer patients and their families despite a campaign by the Irish Cancer Society.
The charity says it's disappointed hospital bosses haven't acted on a call for free or subsidised fees for those undergoing chemotherapy or radiation treatment.
Spokesperson Rachel Foley says "while cancer patients were struggling to pay for car parking, at the same time the Dublin hospitals were actually increasing their revenue raised from car parking. That amounted to €8.75 million across three hospitals last year.
A patient or family members could be going two or three times a week, for a number of weeks or months. One cancer patient told us that his wife had spent €1200 over the course of his treatment at one Dublin hospial."