The Duchess of Cambridge said a charity held a "very special place for me" as she opened its new treatment centre to help people beat addiction.
Wearing a blue Goat coat, Kate unveiled a plaque to officially open Action on Addiction's centre in Wickford, Essex.
The duchess, who is patron of the charity, said: "It seems like a long time ago since I first got involved with Action on Addiction, I think it's about six years ago, but they have a very special place for me and were really the starting of my learning particularly with now the development into mental health.
"So you are very special to me, it's great to be here and actually seeing the development of where the charity's gone in the years gone past.
"Huge congratulations - I believe so passionately in community projects so I wish it all the best of success in the future."
She earlier met with staff and people at different points of their recovery during a visit to the community-based facility.
The centre, which opened its doors to clients last year, hosts a rolling cycle of nine-week long self-help addiction recovery programmes called Clouds in the Community.
The community-based programmes are described as an effective alternative to residential treatment and allow the charity to provide services in more places and to help more people.
Clouds in the Community serves as a starting point for long-term recovery and abstinence, leading to improvements in participants' physical and mental health and overall quality of life.
Action on Addiction said independent evaluation of its Essex programme showed almost 80% of clients did not return to any treatment service after completing the scheme.
The charity has several sites around the country, including its flagship Clouds House centre in Wiltshire which offers residential treatment, and a further community-based site in Liverpool.
It treats all forms of addiction including alcoholism, drug addiction, gambling addiction, sex addiction and food-related disorders.