AIM: To clarify the differences in views on forensic mental health (FMH) systems between the United Kingdom and Japan. METHODS: We conducted a series of semi-structured interviews with six leading forensic psychiatrists. Based on a discussion by the research team, we created an interview form. After we finished conducting all the interviews, we qualitatively analyzed their content. RESULTS: In the United Kingdom the core domain of FMH was risk assessment and management; however, in Japan, the core domain of FMH was psychiatric testimony. In the United Kingdom, forensic psychiatrists were responsible for ensuring public safety, and psychopathy was identified as a disease but deemed as not suitable for medical treatment. On the other hand, in Japan, psychopathy was not considered a mental illness. CONCLUSION: In conclusion, there are considerable differences between the United Kingdom and Japan with regard to the concepts of FMH. Some ideas taken from both cultures for better FMH practice were suggested.