The paper presents an analysis of possibilities of performing recidivism risk assessment under the Act of 22 November 2013 on the treatment of people with mental disorders posing a threat to life, health or sexual freedom of others. The Act allows, among others, the post-penitentiary isolation of persons posing a threat. The risk assessment at “very high” level is one of the key elements taken into account in adjudication of this procedure.The first part presents basic information on the recidivism risk assessment procedure: types of risk factors and different approaches to recidivism risk assessment. Then, three main limitations related to the assessment under the Act were discussed. These are: (1) the problem of the scope of the predicted events, (2) the problem of differentiation between the upper sub-categories of recidivism risk, (3) the problem of the lack of full Polish adaptations of recidivism risk assessment instruments. In consequence of these limitations, the risk assessment under the Act has lower precision. The problem of the lack of Polish adaptations can be solved with validation of the appropriate instruments. However, the other two challenges result directly from the provisions of the Act and cannot be faced with its current form. Therefore main conclusion of the paper focuses on the need to take into account the discussed limitations by experts, officials participating in the proceedings and the institutions issuing decisions. Risk assessment should be based on the measurement of all types of recidivism risk factors, including primarily static and then stable dynamic ones.