In contemporary criminal law, a prison sentence is the basic and most important type of criminal sanction imposed on criminal offenders in order to prevent and combat crime. In addition to the unconditional prison sentence, all criminal legislations also recognize different modalities of its imposition or execution. Different forms of substitute or alternative measures are awarded in cases where unconditional detention is not necessary. Thus, we can distinguish full or partial suspension of the prison sentence or some other kind of punishment. In the first case, it involves the suspended sentence. This is a complete exemption from the execution of a court-awarded prison sentences (and/or other types and forms of punishment), or determined for a specified time (probation period) and under certain conditions. In case the conditionally convicted person does not meet the set of general and special, mandatory or optional requirements, criminal law provides for mandatory or optional revocation of the suspended sentence. However, in addition to the suspended sentence as a form or modality of executing the imposed prison sentences, some modern criminal laws also recognize the suspended sentence as a special kind of criminal penalty - as a measure of warning. A prerequisite for the implementation of these measures is the fulfillment of the formal requirements, pertaining to the type of offence and prison sentence duration, or material conditions - the court assessment that the application of penalties in the particular case is not necessary because the goals (purpose) of punishment can be achieved without effective enforcement of prison sentences in whole or in part. This paper discusses the concept, characteristics, conditions and methods of implementation of these forms of prison sentence suspension, with various systems of probation supervision in the European criminal law.