Objective: To assess participation and health-related quality of life in adults with bilateral spastic cerebral palsy, and explore associations with self-efficacy. Design: Cross-sectional study. Subjects: A sample of 56 adults with bilateral spastic cerebral palsy (mean age 36.4 (standard deviation 5.8) years; 62% male). Methods: Daily activities and social participation (Life Habits 3.0), health-related quality of life (SF-36 Health Survey), demographic and clinical characteristics, and self-efficacy (General Self-Efficacy Scale (GSES-12)) were assessed. Associations were studied using multivariate logistic regression analyses. Results: At least 60% of the sample had difficulties with mobility, recreation and housing, and 44% had difficulty with personal care and employment. They perceived low health-related quality of life for physical functions, but not for mental functions. Corrected for demographic and clinical characteristics, general self-efficacy explained 49% of the variance in outcome on social participation, and the sub-scale Effort (GSES-12) 32% of the variance for the physical health-related quality of life and 16% of the mental health-related quality of life. Conclusion: A significant number of adults with bilateral spastic cerebral palsy encountered difficulties in social participation and had a low perceived health-related quality of life for physical functions. Higher general self-efficacy or a greater willingness to expend effort in achieving behaviour was related to better participation and a higher physical and mental health-related quality of life.