Stroke victims in Slough and the Royal Borough will have to go to Wycombe or Chertsey after Wexham Park Hospital closed its acute stroke unit on Sunday.
The change has been led by the East Berkshire Clinical Commissioning Groups, who are responsible for planning healthcare in the region.
The decision is supported by NHS Frimley Health Foundation Trust, which manages Wexham Park Hospital.
It says patients will receive better treatment because Wycombe Hospital and Chertsey's St Peter's Hospital have hyper acute stroke units, which Wexham Park Hospital does not.
Director of strategy and operations for the East Berkshire Clinical Commissioning Groups, Fiona Slevin-Brown, said: "The new stroke service will give people the best possible care, as people suspected of having a stroke will be taken straight to the nearest hyper acute stroke unit by ambulance."
She said patients' survival chances would greatly increase as they would be more likely to reach hyper acute units within the first hour after symptoms start, which is known as the 'golden hour'.
Despite the better care, the change will mean longer journeys for Slough and Windsor residents.
Wycombe Hospital is just under 18 miles away from central Slough, which is two miles from Wexham Park Hospital.
Central Windsor is just over 18 miles away from Wycombe Hospital and just over 10 miles from St Peter's Hospital, compared to 6 miles to Wexham Park Hospital.
The journey from Maidenhead to Wycombe hospital is only two miles more than the 10 mile trip to Wexham Park Hospital.
The Royal Borough of Windsor and Maidenhead's opposition leader Councillor Lynne Jones (Ind, Old Windsor) said she welcomes the move provided the hospitals are prepared to receive the 200 to 250 stroke patients Wexham Park Hospital receives each year.
She added her concerns over logistics would be alleviated if ambulance drivers are clear on which hospitals would be the nearest for people in each area.
Wexham Park Hospital's stroke unit will now be used as a 12-bed stroke rehabilitation centre.
Whether or not patients will be sent to Wexham Park Hospital for rehabilitation will be decided on a case by case basis depending on their needs and where they live.
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