The headquarters of the trust was in Glangwili General Hospital, Carmarthen.
The Hywel Dda Health Board HQ is in Haverfordwest.
The trust served around 170,000 people across Carmarthenshire and neighbouring counties.
The chairman was Mrs Margaret Price, and the chief executive was Paul Barnett.
It merged with Ceredigion & Mid Wales NHS Trust and Pembrokeshire & Derwen NHS Trust in April 2008.