Cost concerns have been raised over the move to scrap charges
A health authority has said it would have to find hundreds of thousands of pounds to run and police free hospital parking.
NHS Highland said Health Secretary Nicola Sturgeon's announcement posed "many challenges" for Raigmore Hospital in Inverness.
Douglas Seago, NHS Highland head of facilities, said: "It costs around £600,000 a year to run the car park at Raigmore Hospital and there is also a need to fund improvements to meet demand on an increasingly busy site.
"Without dedicated income from motorists we will have to find the money from existing budgets.
"We will work with our staff representatives and others to consider how we will deter people who have no business at the hospital from taking up spaces needed by patients."
He added: "It is difficult to see how we can do this without employing wardens at additional cost. We do receive complaints about the car park but the majority are because it takes people some time to find a space and not about the charge."
Vistors and patients pay £1 on exit, while staff are charged depending on how much they earn.
Those who earn under £6.01 per hour pay £52 a year, those who earn more than £6.01 and up to £30k p/a pay £72 a year and those who earn more than £30k p/a pay £90 a year.
Frequent visitors are offered a weekly car park fob for £7. Disabled car parking is free.
NHS Greater Glasgow and Clyde said it would begin planning for the introduction of free parking.
Meanwhile, NHS Lothian said it had already done "a great deal of work" to reduce charges at the Royal Infirmary of Edinburgh.
John Jack, director of facilities, said: "We will be putting plans in place between now and December to continue to provide car parking for the benefit of our patients.
"All monies raised from the car parking charges are used to provide safe and well-lit parking facilities for our patients.
"One of the major costs is local authority rates and that may be an area of future discussion. We know that we will be facing a challenge in managing traffic at our Edinburgh sites, particularly those sites which are in or close to local authority controlled car parking zones."