Heathrow Terminals 1, 2, 3 and 4 were rated worst by the survey
Passengers have rated Heathrow's Terminal 1 as the worst place to travel from in a survey carried out by Which? Holiday magazine.
Only 31% of the 9,000 people questioned said they were satisfied with services at the west London airport.
Terminals 2, 3 and 4 were listed as the next least popular, followed by Gatwick Airport's two terminals.
BAA, which owns both airports, said it planned to invest £6bn over the next five years to improve infrastructure.
London City airport was rated second best in the survey, after Blackpool's airport, while Heathrow's Terminal 5 came midway in the poll.
About a quarter of all passengers said they found the experience of travelling through an UK airport stressful, but in the case of Heathrow Terminal 1, the figure was between 38 and 45%.
About 19% of those surveyed said they felt intimidated by security staff at Terminal 2.
Many passengers rated signs and flight details at Heathrow Terminals 1 to 4, Manchester's Terminal 1 and Coventry airport as poor.
But Heathrow's new Terminal 5, which faced criticism for its chaotic opening last year, fared better in the survey, with 54% of people saying they were satisfied with services there.
London City came as the second best in the survey
Regional airports won accolades, with eight out of 10 travellers saying they were happy with services at Blackpool airport, followed by London City airport at 78%, Doncaster Sheffield (76%) and Southampton 71%.
Which? Holiday editor Lorna Cowan said the survey showed passengers "prefer the experience of flying from smaller regional airports".
"But people still need to use Gatwick and Heathrow for long-haul trips. Our results suggest that these large airports need to work much harder to provide a better service for their passengers."
BAA said: "Over the next five years, BAA will spend over £6 billion to improve airport infrastructure and ensure that our passengers experience better service. In recent months, our service levels have improved markedly."