Assessing and targeting substance abuse-related treatment needs according to evidence-based practice has become the norm in most prison administrations. Not everyone with a need will, however, receive support in practical settings. Drawing on Finnish prison registers, we show that of all prisoners released in 2011, 60% were assessed as having a need for substance abuse-related support. Of these, 22% received an intervention in prison. Two multivariate models were used to examine the factors related to selection into interventions. The main factors associated with receiving an intervention with evidence-based programmes were a longer sentence, Finnish nationality, younger age and treatment motivation. The predictors for any substance abuse interventions (including non-evidence-based) were the same, with the exception that motivation was no longer a significant predictor, and female gender remained significant. The selective use of motivation as an entrance criterion for interventions can be a means of systemic adaptation to a combination of a high prevalence of substance abuse problems and a lower prevalence of treatment motivation in the prison population. We discuss how our results might reflect a Scandinavian way of doing evidence-based, prison-based drug treatment-one that stresses rehabilitation as a goal in itself in addition to reducing recidivism. Most prisoners, however, do not receive any intervention at all.