This paper focuses on investigating public attitudes towards mentally disordered offenders (MDOs), by considering if the Police and Community Attitudes towards Offenders with Mental Illness (PACAMI-O; Glendinning and O’Keeffe in J Mental Health Train Educ Pract 10(2):73–84, 2015) is a valid tool. An opportunity sample of the general public (N = 504) read a fictional vignette depicting an individual with schizophrenia, then answered the PACAMI-O. An exploratory factor analysis revealed a 4 factor solution: Social distance & location of Services, Mental Health Spending, Attitudes towards Psychiatric Facilities and Community Acceptance. The results suggested that 12 items in the PACAMI-O did not contribute towards measuring public attitudes. Therefore 28 items were retained for the new, more concise, valid scale; Public Attitudes towards Offenders with Mental Illness (PATOMI). PATOMI can be used in future research to effectively assess public attitudes. Application, limitations and suggestions for future research are discussed.