BACKGROUND: The volatile HIV epidemic in Moldova, driven primarily by people who inject drugs (PWIDs), is concentrated in prisons. Although internationally recommended opioid agonist therapy (OAT) is available in Moldovan prisons, coverage remains inadequate and expansion efforts have failed to meet national and international goals.<br/> METHODS: To better understand why eligible prisoners are reluctant to initiate OAT, we surveyed recently released prisoners who met criteria for opioid dependence and compared those who had and had not been enrolled in within-prison OAT (N=56) using standardized scales on OAT knowledge and attitudes as well as within-prison harassment experiences.<br/> RESULTS: Knowledge about OAT was similar between both groups, but this knowledge and myths about OAT had independent and opposite direct effects on OAT attitudes. Those who were enrolled in OAT in prison were significantly more likely to perceive it as an effective form of treatment and had more tolerable attitudes toward OAT but were also more likely to have been bullied and to express concerns about their personal safety. Prisoners who had not been enrolled in OAT were more likely to endorse negative myths about methadone; only one person among them intended to receive OAT in the future.<br/> CONCLUSION: In Moldovan prisons, OAT enrollment and treatment continuation are influenced by ideological biases and myths that are largely formed, amplified, and reinforced behaviorally in restricted prison settings. Future interventions that expand OAT in prisons should target individual-level ideological prejudices and myths, as well as the prison environment.<br/>