Background: Forensic psychiatric practices and provisions vary considerably across jurisdictions. The diversity provides the possibility to compare forensic psychiatric practices, as we will do in this paper regarding Italy and the Netherlands. Aim: We aim to perform a theoretical analysis of legislations dealing with the forensic psychiatric evaluation of defendants, including legal insanity and the management of mentally ill offenders deemed insane. This research is carried out not only to identify similarities and differences regarding the assessment of mentally ill offenders in Italy and the Netherlands, but, in addition, to identify strengths and weaknesses of the legislation and procedures used for the evaluation of the mentally ill offenders in the two countries. Results: Italy and the Netherlands share some basic characteristics of their criminal law systems. Yet, forensic psychiatric practices differ significantly, even if we consider only evaluations of defendants. A strong point of Italy concerns its test for legal insanity which defines the legal norm and enables a straightforward communication between the experts and the judges on this crucial matter. A strong point of the Netherlands concerns more standardized practices including guidelines and the use of risk assessment tools, which enable better comparisons and scientific research in this area. Conclusions: We argue that there appears to be room for improvement on both sides with regards to the evaluation of mentally ill offenders. More generally, a transnational approach to these issues, as applied in this paper, could help to advance forensic psychiatric services in different legal systems.