<p>This study compared the psycho–social characteristics of newly entered inmates to penal institutions across Japan with and without partial suspension of execution committed simulant drug related offenses. Inmates with partial suspension of execution were significantly more likely than those without to report engaged experiences in medical care and peer support, criminal history by substance use offences, psychiatric comorbidity and early first time simulant drug use. Furthermore, inmates with partial suspension of execution were found to have a higher degree of problems related to drug use measured by The Drug Abuse Screening Test-20 (DAST-20) than those without. Additionally, results from decision tree analyses indicated that some psycho–social characteristics influence judicial sentencing about imprisonment with partial suspension of execution. The groups with psycho–social characteristics that are likely to be inmates with partial suspension of execution had higher severity of drug use problems than those without them. In the light of these findings, justice decision making of imprisonment with partial suspension of execution seems to be determined with sufficient consideration of treatment needs and responsivity for preventing reoffending.</p><p>This study compared the psycho–social characteristics of newly entered inmates to penal institutions across Japan with and without partial suspension of execution committed simulant drug related offenses. Inmates with partial suspension of execution were significantly more likely than those without to report engaged experiences in medical care and peer support, criminal history by substance use offences, psychiatric comorbidity and early first time simulant drug use. Furthermore, inmates with partial suspension of execution were found to have a higher degree of problems related to drug use measured by The Drug Abuse Screening Test-20 (DAST-20) than those without. Additionally, results from decision tree analyses indicated that some psycho–social characteristics influence judicial sentencing about imprisonment with partial suspension of execution. The groups with psycho–social characteristics that are likely to be inmates with partial suspension of execution had higher severity of drug use problems than those without them. In the light of these findings, justice decision making of imprisonment with partial suspension of execution seems to be determined with sufficient consideration of treatment needs and responsivity for preventing reoffending.</p>