By accessing addiction treatment services recorded in routine national drug treatment data, the characteristics of Irish Travellers were analyzed to understand their needs and develop policies to tackle issues faced by this community. The number of Traveller cases accessing services increased by 163% between 2007 and 2010. Alcohol and opiates were the most common problem substances reported. Traveller women reported high rates of problem opiate use and risky injecting behaviors, contrary to the perception that problem substance use is a predominantly male issue. This presents a challenge to services to provide targeted, effective services to Travellers with problem substance use.