The article discusses the issue concerning the implementation of the principle of treating a penalty of deprivation of liberty as ultima ratio in the practice of justice administration. The statutory solutions adopted in the original version of the Criminal Code of 1997 are the starting point of the analysis. It shows a new approach to the penalty of deprivation of liberty, which – as it was assumed – was to become a subsidiary penalty applied to petty crime. In practice, it turned out that an attempt to minimise the role of the penalty of deprivation of liberty in the penal policy was a failure, which resulted in a considerable size of prison population and a big number of offenders convicted and waiting for the penalty execution. A penalty of deprivation of liberty with conditional suspension of its execution adjudicated on a massive scale remained the basic means of penal response to petty crime. The diagnosis of the reasons for the actual situation became the basis for the criminal law reform of 2015. The article discusses the most important amendments to the provisions of the Criminal Code, which are to contribute to the increase in the importance of non-custodial penalties (a fine and a penalty of deprivation of liberty) and to limit the scope of application of the penalty of deprivation of liberty (its absolute type and with conditional suspension of its execution). The statistical overview of the penalty of absolute deprivation of liberty and the penalty of deprivation of liberty with conditional suspension of its execution presented in the article makes the author draw a conclusion that the penalty of deprivation of liberty is still treated as ultima ratio in the practice of justice administration. Despite a considerable decrease in the importance of the penalty of deprivation of liberty with conditional suspension of its execution in the penal policy and a growing share of non-custodial penalties in the structure of adjudicated penalties, the share of the penalty of absolute deprivation of liberty in all convictions is growing and the number of adjudicated and not executed penalties of absolute deprivation of liberty is also higher. That is why, the author expresses an opinion that failure in the implementation of the penal policy assumptions of the 2015 criminal law reform results from too drastic limitation of a possibility of applying the penalty of deprivation of liberty with conditional suspension of its execution. Therefore, she supports the proposals expressed in literature to extend grounds for adjudicating the penalty of deprivation of liberty with conditional suspension of its execution.