Hospitals have been told to improve standards despite inspectors finding most were clean.
However, patients can expect food that was only considered "acceptable" rather than "good" at many hospitals.
The verdict comes from inspectors commissioned by the Department of Health to check all hospitals in Sussex.
Almost 30 acute, mental health and community hospitals were assessed by patient environment action teams.
Each hospital was given either a red (poor), amber (acceptable) or green (good) rating for their food and for how clean they were.
Results published today show the food given to patients in all the county's hospitals is acceptable - which means more work needs to be done.
This is the first time food standards have been assessed.
No hospital in the county was found to be so dirty it was given a poor rating but 16 were classed as acceptable while 12 were given the highest, green rating.
Princess Royal Hospital in Haywards Heath was the only one to drop its standards, going from good to acceptable.
Southlands Hospital in Shoreham has shown a marked improvement, rising from a red rating in 2001 to green.
Worthing Hospital has also cleaned up its act, going from acceptable to good.
Other hospitals given a green rating were the Royal Alexandra Hospital for Sick Children in Brighton, Eastbourne District General Hospital, the Conquest Hospital in Hastings, St Richard's hospital in Chichester and the Queen Victoria Hospital in East Grinstead.
Those on amber include the Royal Sussex County Hospital in Brighton, Crawley Hospital and Brighton General.
A spokesman for the Patient Action Group in Sussex said the report was encouraging.
She said: "We have had concerns raised by patients about the standard of cleanliness in some hospitals, with complaints about dirty and untidy wards.
"We hope these inspections will continue and the hospitals are regularly checked to make sure they make any necessary improvements."
The ratings are part of a national campaign by the Department of Health to clean up hospitals and improve conditions for patients.
They show 60 per cent of hospitals in England are now classed as having good standards of cleanliness, 40 per cent are amber and none are red.
This is an improvement on three years ago when 35 per cent of hospitals were considered to have poor levels of cleanliness.
Health Minister Lord Hunt said: "The £60 million clean up campaign is working but we are not complacent about the continuing need to drive forward these reforms."
The next stage of the better hospital food programme will involve an extension of the food inspection scheme.
Food and drink services in accident and emergency departments will be expanded and more financial support will be given to catering services run by voluntary groups in hospitals.
Cleanliness standards for 2003 will become more rigorous and include more hospital equipment.
A spokesman for Brighton and Sussex University Hospitals NHS Trust said staff were surprised the rating for Princess Royal Hospital had dropped and they would wait to investigate the report in more detail to find out what had happened.
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