Personality disorder is common amongst individuals accessing mental health services, with research into its aetiology and impact on services increasing in recent years. This thesis has two parts. The first is a systematic review of the neuropsychological functioning among forensic samples with diagnoses of psychopathy and antisocial personality disorder (ASPD). Five databases were searched for cross-sectional studies exploring cognitive functioning in psychopathy and ASPD. Twelve studies were reviewed and indicated that individuals with psychopathy and ASPD demonstrate deficits in executive functions, attention, and memory, and that there are some differences in neuropsychological performance between the two disorders. The second part is an empirical study exploring factors that may influence mental health staff attitudes towards individuals with personality disorder. The study found that staff personality traits, emotion regulation style, empathy and job satisfaction were related to attitudes to personality disorder. Empathy and job burnout predicted attitudes, with higher scores on empathy and lower levels of burnout being related to positive attitudes to personality disorder. Implications for the findings of the systematic review and empirical study are discussed. Further research is required in both areas.