The aim of this research is to determine the phenolic acids in three types of Irish whiskies, multiple whiskey types from the same distillery, single malt whiskies from the one distillery aged in different casks and a range of single pot still whiskies unique to Ireland, to ascertain the impact on the phenolic acid profile of the aging length, aging process and whiskey mashbill. Whiskey samples were injected directly onto the capillary and preconcentrated using field amplified sample stacking prior to analysis with capillary electrophoresis using ultraviolet detection. It was shown that the phenolic aldehydes vanillin and syringaldehyde increased in concentration with aging, while in whiskies aged in sherry casks, a greater number of phenolic compound types were observed and aging in bourbon casks also resulted in distinctive profiles. It was also shown that single pot still whiskeys contained phenolic compound profiles which were typically rich in phenolic aldehyde concentrations and a diversity of phenolic acids. This is the first time that phenolic acid profiles, which contribute to the beverage flavour, have been characterised for single pot still whiskies.