13 people in Mayo and 33 in Galway were treated for cocaine addiction last year.
New figures published by the Health Research Board show 13 people in Mayo presented with cocaine addiction issues in Co Mayo in 2019 - down from 16 the previous year.
In Galway, 33 people accessed drug treatment services last year, which was more than double the previous year.
17 people in both Roscommon and Sligo accessed cocaine addiction services last year.
The Health Research Board has found that, for the first time, cocaine has overtaken cannabis as the second most common drug that people enter treatment for, while heroin tops the list.