The aim of this research was to determine the relationship between personality characteristics of prisoners and the course of their prison sentence. For this purpose there were two research problems. The first was to determine the characteristics of the course of their prison sentence and the other to examine the differences in the dimensions of the Eysenck’s inventory impulsivity due to the different characteristics of the course of serving the prison sentence. The sample consists of convicted criminal offenders who came in the Center for Diagnostics in Zagreb during 2013. To answer the problem questions, the results obtained in the Eysenck’s impulsivity inventory were used. It measures three personality traits (impulsivity, adventure and empathy). The data from the personal file of prisoners concerning the course of serving their prison sentence was also used. The results showed that the highest number of prisoners came out of the same conditions as those in which they have entered, more prisoners worked during, most did not educate themselves while serving the sentence, they spent their free time non structured and have had contact with the outside world. A large number of prisoners attended special treatment programs, used benefits outside the prison, had no disciplinary infractions and more than half of them were released on parole. Statistically significant differences in Eysenck’s impulsivity inventory existed between the prisoners who worked and who did not work in a way that those who did work during their prison sentence have lower scores on impulsiveness and venturesomeness. When it comes to other variables, no statistically significant differences in the dimensions of Eysenck’s impulsivity inventory were found.