PURPOSE: To assess the level and potential determinants of everyday physical activity and participation in various life areas of adults with hemiplegic cerebral palsy (CP) in comparison with healthy subjects. METHOD: In a cross-sectional study everyday physical activity was measured (Activity Monitor) in 16 adults with CP, aged 28 (3) years, and 16 age/gender matched healthy volunteers, aged 29 (3) years. Participation was assessed by means of validated questionnaires. Age, gender, body fat (skinfold thickness), muscle tone (Ashworth Scale), functional level and participation were assessed as potential determinants of everyday physical activity. RESULTS: In adults with CP mean (SD) duration of dynamic activities during a day (10.6 [3.5]%) was comparable to healthy subjects (11.2 4%) (p = 0.66). In most life areas the level of participation was comparable for both groups, although adults with CP spent more time on non-intensive leisure activities. Participation in sports appeared to be a determinant of everyday physical activity in both groups. CONCLUSIONS: The results indicate that the levels of everyday physical activity and community participation in adults with hemiplegic CP are comparable to levels in healthy comparison subjects