In Germany, Austria and Switzerland, lawbreakers who are unwilling or unable to pay a fine for committing a criminal offence can face imprisonment. The length of compensation imprisonment corresponds to the amount of the fee the convicted was sentenced to pay. Every tenth German prisoner serves this kind of sentence. Recent meta-analyses indicated that inmates are several times more likely to suffer from psychosis and major depression and are more than ten times more likely to exhibit antisocial personality disorders than the general population. This study set out to assess the levels of mental disorders in the population of compensation prisoners in the German capital Berlin in 1999, 2004, 2010 and 2017.The four study populations, consisting of 100 participants each, showed a high prevalence of mental disorders and were therefore mostly unable to apply for serving voluntary work as alternative to imprisonment. As the prevalence of mental disorders was largely consistent over the investigation timeframe, it seems advisable to make a psychopathological diagnosis at the start of imprisonment in order to filter out those detainees that would benefit from social training in order to enhance their competency to solve problems, strengthen their social skills and enhance their quality of life outside of the penal institution. In addition, as the compensation prisoners exhibited a high degree of substance abuse, it would be recommendable to assess the presence of substance abuse at the beginning of imprisonment. Then, appropriate measures could be taken to reduce the number of reoffenders and enable the temporary detainees to reintegrate successfully into society.