One of the biggest causes of complaint has been the high charges some hospitals make for car-parking.
Now, using the Freedom of Information Act, the BBC has found out exactly how much hospitals in England are making from the charges.
The figures - obtained from the Department of Health - reveal that some hospitals generate more than £1m from parking fees, while others make only a few thousand pounds.
You can see the full list of hospital income from car-parks via the link below. You will need to have a PDF reader installed on your computer
We took the decision to remove a handful of hospitals from the list, because they appeared to have given inaccurate figures (two appeared to suggest they had made £6 in a year).
And, although the information was gathered by the Department of Health, not every hospital in England responded to its request for information.
The data collected is for 2004 to 2005, but the Department of Health told Breakfast "This is a non-mandatory collection and therefore may not be complete."
The figures represent the total gross income generated by parking fees - before costs such as staff and maintenance.
Crunching the numbers
The University Hospital Birmingham said it received £1.5m in car parking charges last year - and paid its contractor Q-Park £1m to operate the car parks.
The hospital says half a million pounds went back to patient care
That leaves half a million pounds, which has been ploughed back into patient care in its hospitals.
The hospital's communications director Fiona Alexander told us that the car park has half a million users a year, paying on average a £3 charge for three hours.
She added that £800,000 has been spent on improving the car park, providing CCTV, shuttle buses and free parking for kidney and cancer patients.
The Birmingham trust is one of twelve hospital trusts in England which generated more than a million pounds in gross income from car-parking last year.
Gerard and Amanda spent £560 on parking when he had leukaemia
The other million-pound money spinners are: Basildon and Thurrock University Foundation Trust; Cambridgeshire University Hospital Trust; North West London Hospitals; Portsmouth Hospitals; Southampton University Hospitals; Barking, Havering and Redbridge Hospitals; Barnet and Chase Farm Hospitals; East Kent Hospitals; Epsom and St Helier; Pennine Acute Hospitals; United Lincolnshire Hospitals.
There's a wide difference between the amount of money generated by car park charges: for instance, Tower Hamlets Primary Care Trust received £5,110.
The Department of Health stressed that it was up to the individual hospital to decide whether to provide a car park and whether to charge. It added:
"What level any charge should be set, taking into account local circumstances including patients, visitors and staff needs and the cost of providing the service".