Alcohol and cannabis are the primary substances contributing to referrals of adolescents to substance abuse treatment services. Their outcome has not been examined in Ireland. A three month follow-up was conducted in an outpatient adolescent treatment program. We followed up 35 high risk users of alcohol and 55 high risk users of cannabis. Although the high risk drinkers achieved a significant reduction in median number of days drinking (p=0.004), only four (11%) were abstinent at follow up. A further five (14%) achieved a reliable reduction in days of drinking. The high risk cannabis users demonstrated a significant drop in median days of use (p<0.001), although only six (11%) were abstinent at follow up. A further 20 (36%) achieved a reliable reduction in days of use. Calculation of reliable change allows examination of outcomes which fall short of the elusive goal of abstinence.