The links between crime and substance abuse have been previously established. The Federal Bureau of Prisons (FBOP) offers an intensive cognitive behavioral residential drug abuse treatment program (RDAP) that addresses inmates' criminal thinking in an attempt to change criminal behaviors including substance abuse. RDAP has been shown to reduce relapse and recidivism. However, not all inmates who qualify for treatment agree to participate despite incentives provided for treatment participation and completion. This dissertation is an exploration of differences in two groups of federal inmates: those who choose to enter residential drug abuse treatment and those to choose to decline treatment. The differences between inmates who accept or decline treatment are explored through variables including criminal thinking as measured by the Psychological Inventory of Criminal Thinking Styles, eligibility for early release, and motivation for change. The study results indicate that inmates who are waiting to enter RDAP report more criminal thinking than inmates who are qualified for treatment but decline RDAP. The inmates waiting to enter RDAP are more likely to report higher scores on the criminal thinking style superoptimism than any other criminal thinking style. Additionally, for those waiting to enter RDAP a significant positive correlation is seen between proactive criminal thinking and eligibility for early release. No differences were found within the RDAP-Decline group. Eligibility for early release and motivation for change were significant predictors of RDAP-status. The dissertation concludes with a discussion of implications for practice and research.