Guernsey's Health Department is asking islanders how successful its mental health and adult well-being programmes are.
More than 3,000 surveys are being sent to a random selection of the adult population of Guernsey and Alderney.
The Health and Social Services Department said it needed a comprehensive benchmark to work from.
Minister Hunter Adam said: "The results of the survey will provide a unique insight into the 'mood of the island'."
Dr Stephen Bridgman, director of public health, said: "Mental health is the biggest cause of health-related disability and is one of the major challenges for public health."
Clinical psychologist and service manager Dr Sara Johnson said: "This survey also offers a unique opportunity for people to express their views on how mental health services, and particularly psychological therapies for adults, should be provided.
"It will enable us to develop better local services specifically to meet these needs."
The Guernsey branch of Mind, a mental health charity, was involved in designing the survey.
Advocacy worker Emily Litten said: "Mental health and well-being is everybody's business and taking part in this survey gives islanders a rare opportunity to play an active role in shaping the care and support available locally.
"I hope that those who receive the survey will take the time to have their say and in doing so give local people with mental health distress the best possible chance of recovery."
The Health Department hopes the random selection will led to "a diverse cross-section of the Bailiwick population" filling out the survey.
It said all answers provided would be treated as confidential and anonymous.