AIM: To examine the most relevant aspects of functioning of adults with cerebral palsy (CP) from their perspective, in order to develop an International Classification of Functioning, Disability and Health (ICF) Core Set for adults with CP. METHOD: We conducted six focus group discussions with adults with CP without intellectual disability and seven interviews with adults with CP with intellectual disability and caregivers, addressing all ICF components. Meaningful concepts were identified from verbatim transcripts and linked to ICF categories by two independent researchers. RESULTS: In total, 31 adults with CP without intellectual disability (mean [SD] age 46y 1mo [14y 1mo]; 20 females, 11 males; Gross Motor Function Classification System [GMFCS] levels I-IV) and seven adults with CP and intellectual disability (mean [SD] age 25y 8mo [6y 8mo]; four females, three males; GMFCS levels III-V) participated. We identified 132 unique second-level categories: 47 body functions, seven body structures, 43 activities and participation, and 35 environmental factors. The most frequently mentioned categories were emotional function, pain, muscle tone function, support of family, products and technology, and health services. INTERPRETATION: Adults with CP experienced problems in a broad range of body functions and activities and indicated the importance of environmental factors for functioning. The identified categories will be added to the list of candidate items to reach consensus on an ICF Core Set for adults with CP. What this paper adds Including the lived experience is crucial for fully understanding functioning of adults with cerebral palsy (CP). Adults with CP perceive environmental factors as essential elements for everyday functioning. Adults with intellectual disability should be considered as a group with specific problems.