Objective To explore the level of difficulty in the activity and participation among persons with disabilities and chronic illnesses in Hong Kong SAR. Methods A cross-sectional study with 954 subjects of disabilities and chronic illnesses based on the WHO Disability Assessment Schedule II (WHODAS 2.0). Results People with disabilities and chronic illnesses were facing moderate to severe level of difficulty in the activity and participation. Their most difficult aspects were found in the domestic responsibilities and social participation. Conclusion The Hong Kong SAR government should explore and adopt the Classification of Functioning, Disability and Health (ICF) framework and take the elements of activity and participation into consideration for the planning and formulation of rehabilitation policies and services which in the long run, help safeguard the rights of persons with disabilities and chronic illnesses and realize the implementation of the Convention on the Rights of Persons with Disabilities.