This paper discusses factors associated with low rates of help-seeking and poorer quality of physical healthcare among people with mental illnesses. Evidence is reviewed on the associations between low rates of mental health literacy, negative attitudes towards people with mental illness, and reluctance to seek help by people who consider that they may have a mental disorder. People with mental illness often report encountering negative attitudes among mental health staff about their prognosis, associated in part with 'physician bias'. 'Diagnostic overshadowing' appears to be common in general health care settings, meaning the misattribution of physical illness signs and symptoms to concurrent mental disorders, leading to underdiagnosis and mistreatment of the physical conditions.