Swansea Bay health board saw the highest proportion spending less than 4 hours in emergency departments (77.3%), and Cardiff and Vale saw the lowest (64.7%).
Bwrdd iechyd Bae Abertawe welodd y gyfran uchaf yn treulio llai na 4 awr mewn adrannau achosion brys (76.6%), ac yng Nghaerdydd a’r Fro oedd y gyfran isaf (63.9%).