Background and purpose: Personality disorders may lead to addiction and viral diseases. On the other hand, addiction and viral infections also cause mental and personality disorders. This research aimed at comparing personality disorders and clinical symptoms between male prisoners.

Materials and methods: A cross–sectional study was conducted in male prisoners in Quchan, Iran, 2014. Three groups (healthy, addict, and viral infection) including 200 prisoners were selected using systematic sampling. Millon Clinical Multiaxial Inventory (MCMI-III) was administered. The multivariate analysis (MANOVA) was applied in SPSS V. 11.5.

Results: There was significant differences between the three groups in schizoid, dependent, histrionic, narcissistic, antisocial, sadistic, and masochistic personality disorders (P<0.001). Significant differences were found between patients and addicts, and healthy prisoners in avoidance, OCD, passive- aggressive, schizotypal and borderline disorders (P<0.001), but this difference were not significant between patients and addicts (P>0.001). In paranoid scale, there was a significant difference between addicts and healthy prisoners (P<0.001), but the difference between other groups was not significant (P>0.001).

Conclusion: Mental disorders were found to be more prevalent in addict prisoners and those with viral infections, therefore, effective psychological interventions are highly recommended for prisoners.