This chapter covers the challenges that those with mental illnesses, substance use disorders, and disabilities experience while incarcerated. Many correctional facilities are underfunded, understaffed, overcrowded, and lack the resources to meet individuals’ physical and mental health care needs. Also covered are the problems associated with a lack of knowledge of mental illnesses and disabilities among correctional staff, which can lead to inappropriate or unnecessary disciplinary actions. This chapter also includes the cognitive factors among those with mental illnesses, intellectual disabilities, and juveniles and the eligibility for capital punishment, with a focus on civil and human rights. The chapter concludes with considerations and recommendations from experts in the field to meet the unique needs of those with mental illnesses and disabilities in correctional institutions.